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.TH "GRDMATH" "1gmt" "May 21, 2019" "5.4.5" "GMT"
.SH NAME
grdmath \- Reverse Polish Notation (RPN) calculator for grids (element by element)
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.SH SYNOPSIS
.sp
\fBgrdmath\fP
[  \fB\-A\fP\fImin_area\fP[/\fImin_level\fP/\fImax_level\fP][\fB+ag\fP|\fBi\fP|\fBs\fP |\fBS\fP][\fB+r\fP|\fBl\fP][\fBp\fP\fIpercent\fP] ]
[  \fB\-D\fP\fIresolution\fP[\fB+\fP] ]
[  \fB\-I\fP\fIincrement\fP ]
[  \fB\-M\fP ] [  \fB\-N\fP ]
[  \fB\-R\fP\fIregion\fP ] [  \fB\-V\fP[\fIlevel\fP] ]
[ \fB\-bi\fPbinary ]
[ \fB\-di\fPnodata ]
[ \fB\-f\fPflags ]
[ \fB\-h\fPheaders ]
[ \fB\-i\fPflags ]
[ \fB\-n\fPflags ]
[ \fB\-r\fP ]
[ \fB\-x\fP[[\-]\fIn\fP] ]
\fIoperand\fP [ \fIoperand\fP ] \fBOPERATOR\fP [ \fIoperand\fP ]
\fBOPERATOR\fP ... \fB=\fP \fIoutgrdfile\fP
.sp
\fBNote:\fP No space is allowed between the option flag and the associated arguments.
.SH DESCRIPTION
.sp
\fBgrdmath\fP will perform operations like add, subtract, multiply, and
divide on one or more grid files or constants using Reverse Polish
Notation (RPN) syntax (e.g., Hewlett\-Packard calculator\-style).
Arbitrarily complicated expressions may therefore be evaluated; the
final result is written to an output grid file. Grid operations are
element\-by\-element, not matrix manipulations. Some operators only
require one operand (see below). If no grid files are used in the
expression then options \fB\-R\fP, \fB\-I\fP must be set (and optionally
\fB\-r\fP). The expression \fB=\fP \fIoutgrdfile\fP can occur as many times as
the depth of the stack allows in order to save intermediate results.
Complicated or frequently occurring expressions may be coded as a macro
for future use or stored and recalled via named memory locations.
.SH REQUIRED ARGUMENTS
.INDENT 0.0
.TP
.B \fIoperand\fP
If \fIoperand\fP can be opened as a file it will be read as a grid file.
If not a file, it is interpreted as a numerical constant or a
special symbol (see below).
.TP
.B \fIoutgrdfile\fP
The name of a 2\-D grid file that will hold the final result. (See
GRID FILE FORMATS below).
.UNINDENT
.SH OPTIONAL ARGUMENTS
.INDENT 0.0
.TP
\fB\-A\fP\fImin_area\fP[/\fImin_level\fP/\fImax_level\fP][\fB+ag\fP|\fBi\fP|\fBs\fP|\fBS\fP][\fB+r\fP|\fBl\fP][\fB+p\fP\fIpercent\fP]
Features with an area smaller than \fImin_area\fP in km^2 or of
hierarchical level that is lower than \fImin_level\fP or higher than
\fImax_level\fP will not be plotted [Default is 0/0/4 (all features)].
Level 2 (lakes) contains regular lakes and wide river bodies which
we normally include as lakes; append \fB+r\fP to just get river\-lakes
or \fB+l\fP to just get regular lakes.  By default (\fB+ai\fP) we select the ice shelf
boundary as the coastline for Antarctica; append \fB+ag\fP to instead
select the ice grounding line as coastline.  For expert users who wish to
print their own Antarctica coastline and islands via \fIpsxy\fP you can
use \fB+as\fP to skip all GSHHG features below 60S or \fB+aS\fP to instead
skip all features north of 60S.  Finally, append
\fB+p\fP\fIpercent\fP to exclude polygons whose percentage area of the
corresponding full\-resolution feature is less than \fIpercent\fP\&. See
GSHHG INFORMATION below for more details. (\fB\-A\fP is only relevant to the \fBLDISTG\fP operator)
.UNINDENT
.INDENT 0.0
.TP
\fB\-D\fP\fIresolution\fP[\fB+\fP]
Selects the resolution of the data set to use with the operator LDISTG
((\fBf\fP)ull, (\fBh\fP)igh, (\fBi\fP)ntermediate, (\fBl\fP)ow, and (\fBc\fP)rude). The
resolution drops off by 80% between data sets [Default is \fBl\fP].
Append \fB+\fP to automatically select a lower resolution should the one
requested not be available [abort if not found].
.UNINDENT
.INDENT 0.0
.TP
\fB\-I\fP\fIxinc\fP[\fIunit\fP][\fB+e\fP|\fBn\fP][/\fIyinc\fP[\fIunit\fP][\fB+e\fP|\fBn\fP]]
\fIx_inc\fP [and optionally \fIy_inc\fP] is the grid spacing. Optionally,
append a suffix modifier. \fBGeographical (degrees) coordinates\fP: Append
\fBm\fP to indicate arc minutes or \fBs\fP to indicate arc seconds. If one
of the units \fBe\fP, \fBf\fP, \fBk\fP, \fBM\fP, \fBn\fP or \fBu\fP is appended
instead, the increment is assumed to be given in meter, foot, km, Mile,
nautical mile or US survey foot, respectively, and will be converted to
the equivalent degrees longitude at the middle latitude of the region
(the conversion depends on PROJ_ELLIPSOID). If \fIy_inc\fP is given
but set to 0 it will be reset equal to \fIx_inc\fP; otherwise it will be
converted to degrees latitude. \fBAll coordinates\fP: If \fB+e\fP is appended
then the corresponding max \fIx\fP (\fIeast\fP) or \fIy\fP (\fInorth\fP) may be slightly
adjusted to fit exactly the given increment [by default the increment
may be adjusted slightly to fit the given domain]. Finally, instead of
giving an increment you may specify the \fInumber of nodes\fP desired by
appending \fB+n\fP to the supplied integer argument; the increment is then
recalculated from the number of nodes and the domain. The resulting
increment value depends on whether you have selected a
gridline\-registered or pixel\-registered grid; see App\-file\-formats for
details. Note: if \fB\-R\fP\fIgrdfile\fP is used then the grid spacing has
already been initialized; use \fB\-I\fP to override the values.
.UNINDENT
.INDENT 0.0
.TP
\fB\-M\fP
By default any derivatives calculated are in z_units/ x(or
y)_units. However, the user may choose this option to convert dx,dy
in degrees of longitude,latitude into meters using a flat Earth
approximation, so that gradients are in z_units/meter.
.UNINDENT
.INDENT 0.0
.TP
\fB\-N\fP
Turn off strict domain match checking when multiple grids are
manipulated [Default will insist that each grid domain is within
1e\-4 * grid_spacing of the domain of the first grid listed].
.UNINDENT
.INDENT 0.0
.TP
\fB\-R\fP\fIxmin\fP/\fIxmax\fP/\fIymin\fP/\fIymax\fP[\fB+r\fP][\fB+u\fP\fIunit\fP] (more ...)
Specify the region of interest.  
.UNINDENT
.INDENT 0.0
.TP
\fB\-V\fP[\fIlevel\fP] (more ...)
Select verbosity level [c].  
.UNINDENT
.INDENT 0.0
.TP
\fB\-bi\fP[\fIncols\fP][\fBt\fP] (more ...)
Select native binary input. The binary input option
only applies to the data files needed by operators \fBLDIST\fP,
\fBPDIST\fP, and \fBINSIDE\fP\&.
.UNINDENT
.INDENT 0.0
.TP
\fB\-di\fP\fInodata\fP (more ...)
Replace input columns that equal \fInodata\fP with NaN.  
.UNINDENT
.INDENT 0.0
.TP
\fB\-f\fP[\fBi\fP|\fBo\fP]\fIcolinfo\fP (more ...)
Specify data types of input and/or output columns.  
.UNINDENT
.INDENT 0.0
.TP
\fB\-g\fP[\fBa\fP]\fBx\fP|\fBy\fP|\fBd\fP|\fBX\fP|\fBY\fP|\fBD\fP|[\fIcol\fP]\fBz\fP[+|\-]\fIgap\fP[\fBu\fP] (more ...)
Determine data gaps and line breaks.  
.UNINDENT
.INDENT 0.0
.TP
\fB\-h\fP[\fBi\fP|\fBo\fP][\fIn\fP][\fB+c\fP][\fB+d\fP][\fB+r\fP\fIremark\fP][\fB+r\fP\fItitle\fP] (more ...)
Skip or produce header record(s).  
.UNINDENT
.INDENT 0.0
.TP
\fB\-i\fP\fIcols\fP[\fB+l\fP][\fB+s\fP\fIscale\fP][\fB+o\fP\fIoffset\fP][,\fI\&...\fP] (more ...)
Select input columns and transformations (0 is first column).
.UNINDENT
.INDENT 0.0
.TP
\fB\-n\fP[\fBb\fP|\fBc\fP|\fBl\fP|\fBn\fP][\fB+a\fP][\fB+b\fP\fIBC\fP][\fB+c\fP][\fB+t\fP\fIthreshold\fP] (more ...)
Select interpolation mode for grids.
.UNINDENT
.INDENT 0.0
.TP
\fB\-r\fP (more ...)
Set pixel node registration [gridline]. Only used with \fB\-R\fP \fB\-I\fP\&.
.UNINDENT
.INDENT 0.0
.TP
\fB\-x\fP[[\-]\fIn\fP] (more ...)
Limit number of cores used in multi\-threaded algorithms (OpenMP required).
.UNINDENT
.INDENT 0.0
.TP
\fB\-^\fP or just \fB\-\fP
Print a short message about the syntax of the command, then exits (NOTE: on Windows just use \fB\-\fP).
.TP
\fB\-+\fP or just \fB+\fP
Print an extensive usage (help) message, including the explanation of
any module\-specific option (but not the GMT common options), then exits.
.TP
\fB\-?\fP or no arguments
Print a complete usage (help) message, including the explanation of all options, then exits.
.UNINDENT
.SH OPERATORS
.sp
Choose among the following 209 operators. "args" are the number of input
and output arguments.
.TS
center;
|l|l|l|.
_
T{
Operator
T}	T{
args
T}	T{
Returns
T}
_
T{
\fBABS\fP
T}	T{
1 1
T}	T{
abs (A)
T}
_
T{
\fBACOS\fP
T}	T{
1 1
T}	T{
acos (A)
T}
_
T{
\fBACOSH\fP
T}	T{
1 1
T}	T{
acosh (A)
T}
_
T{
\fBACOT\fP
T}	T{
1 1
T}	T{
acot (A)
T}
_
T{
\fBACSC\fP
T}	T{
1 1
T}	T{
acsc (A)
T}
_
T{
\fBADD\fP
T}	T{
2 1
T}	T{
A + B
T}
_
T{
\fBAND\fP
T}	T{
2 1
T}	T{
B if A == NaN, else A
T}
_
T{
\fBARC\fP
T}	T{
2 1
T}	T{
Return arc(A,B) on [0 pi]
T}
_
T{
\fBAREA\fP
T}	T{
0 1
T}	T{
Area of each gridnode cell (in km^2 if geographic)
T}
_
T{
\fBASEC\fP
T}	T{
1 1
T}	T{
asec (A)
T}
_
T{
\fBASIN\fP
T}	T{
1 1
T}	T{
asin (A)
T}
_
T{
\fBASINH\fP
T}	T{
1 1
T}	T{
asinh (A)
T}
_
T{
\fBATAN\fP
T}	T{
1 1
T}	T{
atan (A)
T}
_
T{
\fBATAN2\fP
T}	T{
2 1
T}	T{
atan2 (A, B)
T}
_
T{
\fBATANH\fP
T}	T{
1 1
T}	T{
atanh (A)
T}
_
T{
\fBBCDF\fP
T}	T{
3 1
T}	T{
Binomial cumulative distribution function for p = A, n = B, and x = C
T}
_
T{
\fBBPDF\fP
T}	T{
3 1
T}	T{
Binomial probability density function for p = A, n = B, and x = C
T}
_
T{
\fBBEI\fP
T}	T{
1 1
T}	T{
bei (A)
T}
_
T{
\fBBER\fP
T}	T{
1 1
T}	T{
ber (A)
T}
_
T{
\fBBITAND\fP
T}	T{
2 1
T}	T{
A & B (bitwise AND operator)
T}
_
T{
\fBBITLEFT\fP
T}	T{
2 1
T}	T{
A << B (bitwise left\-shift operator)
T}
_
T{
\fBBITNOT\fP
T}	T{
1 1
T}	T{
~A (bitwise NOT operator, i.e., return two\(aqs complement)
T}
_
T{
\fBBITOR\fP
T}	T{
2 1
T}	T{
A | B (bitwise OR operator)
T}
_
T{
\fBBITRIGHT\fP
T}	T{
2 1
T}	T{
A >> B (bitwise right\-shift operator)
T}
_
T{
\fBBITTEST\fP
T}	T{
2 1
T}	T{
1 if bit B of A is set, else 0 (bitwise TEST operator)
T}
_
T{
\fBBITXOR\fP
T}	T{
2 1
T}	T{
A ^ B (bitwise XOR operator)
T}
_
T{
\fBCAZ\fP
T}	T{
2 1
T}	T{
Cartesian azimuth from grid nodes to stack x,y (i.e., A, B)
T}
_
T{
\fBCBAZ\fP
T}	T{
2 1
T}	T{
Cartesian back\-azimuth from grid nodes to stack x,y (i.e., A, B)
T}
_
T{
\fBCDIST\fP
T}	T{
2 1
T}	T{
Cartesian distance between grid nodes and stack x,y (i.e., A, B)
T}
_
T{
\fBCDIST2\fP
T}	T{
2 1
T}	T{
As CDIST but only to nodes that are != 0
T}
_
T{
\fBCEIL\fP
T}	T{
1 1
T}	T{
ceil (A) (smallest integer >= A)
T}
_
T{
\fBCHICRIT\fP
T}	T{
2 1
T}	T{
Chi\-squared critical value for alpha = A and nu = B
T}
_
T{
\fBCHICDF\fP
T}	T{
2 1
T}	T{
Chi\-squared cumulative distribution function for chi2 = A and nu = B
T}
_
T{
\fBCHIPDF\fP
T}	T{
2 1
T}	T{
Chi\-squared probability density function for chi2 = A and nu = B
T}
_
T{
\fBCOMB\fP
T}	T{
2 1
T}	T{
Combinations n_C_r, with n = A and r = B
T}
_
T{
\fBCORRCOEFF\fP
T}	T{
2 1
T}	T{
Correlation coefficient r(A, B)
T}
_
T{
\fBCOS\fP
T}	T{
1 1
T}	T{
cos (A) (A in radians)
T}
_
T{
\fBCOSD\fP
T}	T{
1 1
T}	T{
cos (A) (A in degrees)
T}
_
T{
\fBCOSH\fP
T}	T{
1 1
T}	T{
cosh (A)
T}
_
T{
\fBCOT\fP
T}	T{
1 1
T}	T{
cot (A) (A in radians)
T}
_
T{
\fBCOTD\fP
T}	T{
1 1
T}	T{
cot (A) (A in degrees)
T}
_
T{
\fBCSC\fP
T}	T{
1 1
T}	T{
csc (A) (A in radians)
T}
_
T{
\fBCSCD\fP
T}	T{
1 1
T}	T{
csc (A) (A in degrees)
T}
_
T{
\fBCURV\fP
T}	T{
1 1
T}	T{
Curvature of A (Laplacian)
T}
_
T{
\fBD2DX2\fP
T}	T{
1 1
T}	T{
d^2(A)/dx^2 2nd derivative
T}
_
T{
\fBD2DY2\fP
T}	T{
1 1
T}	T{
d^2(A)/dy^2 2nd derivative
T}
_
T{
\fBD2DXY\fP
T}	T{
1 1
T}	T{
d^2(A)/dxdy 2nd derivative
T}
_
T{
\fBD2R\fP
T}	T{
1 1
T}	T{
Converts Degrees to Radians
T}
_
T{
\fBDDX\fP
T}	T{
1 1
T}	T{
d(A)/dx Central 1st derivative
T}
_
T{
\fBDDY\fP
T}	T{
1 1
T}	T{
d(A)/dy Central 1st derivative
T}
_
T{
\fBDEG2KM\fP
T}	T{
1 1
T}	T{
Converts Spherical Degrees to Kilometers
T}
_
T{
\fBDENAN\fP
T}	T{
2 1
T}	T{
Replace NaNs in A with values from B
T}
_
T{
\fBDILOG\fP
T}	T{
1 1
T}	T{
dilog (A)
T}
_
T{
\fBDIV\fP
T}	T{
2 1
T}	T{
A / B
T}
_
T{
\fBDUP\fP
T}	T{
1 2
T}	T{
Places duplicate of A on the stack
T}
_
T{
\fBECDF\fP
T}	T{
2 1
T}	T{
Exponential cumulative distribution function for x = A and lambda = B
T}
_
T{
\fBECRIT\fP
T}	T{
2 1
T}	T{
Exponential distribution critical value for alpha = A and lambda = B
T}
_
T{
\fBEPDF\fP
T}	T{
2 1
T}	T{
Exponential probability density function for x = A and lambda = B
T}
_
T{
\fBERF\fP
T}	T{
1 1
T}	T{
Error function erf (A)
T}
_
T{
\fBERFC\fP
T}	T{
1 1
T}	T{
Complementary Error function erfc (A)
T}
_
T{
\fBEQ\fP
T}	T{
2 1
T}	T{
1 if A == B, else 0
T}
_
T{
\fBERFINV\fP
T}	T{
1 1
T}	T{
Inverse error function of A
T}
_
T{
\fBEXCH\fP
T}	T{
2 2
T}	T{
Exchanges A and B on the stack
T}
_
T{
\fBEXP\fP
T}	T{
1 1
T}	T{
exp (A)
T}
_
T{
\fBFACT\fP
T}	T{
1 1
T}	T{
A! (A factorial)
T}
_
T{
\fBEXTREMA\fP
T}	T{
1 1
T}	T{
Local Extrema: +2/\-2 is max/min, +1/\-1 is saddle with max/min in x, 0 elsewhere
T}
_
T{
\fBFCDF\fP
T}	T{
3 1
T}	T{
F cumulative distribution function for F = A, nu1 = B, and nu2 = C
T}
_
T{
\fBFCRIT\fP
T}	T{
3 1
T}	T{
F distribution critical value for alpha = A, nu1 = B, and nu2 = C
T}
_
T{
\fBFLIPLR\fP
T}	T{
1 1
T}	T{
Reverse order of values in each row
T}
_
T{
\fBFLIPUD\fP
T}	T{
1 1
T}	T{
Reverse order of values in each column
T}
_
T{
\fBFLOOR\fP
T}	T{
1 1
T}	T{
floor (A) (greatest integer <= A)
T}
_
T{
\fBFMOD\fP
T}	T{
2 1
T}	T{
A % B (remainder after truncated division)
T}
_
T{
\fBFPDF\fP
T}	T{
3 1
T}	T{
F probability density function for F = A, nu1 = B, and nu2 = C
T}
_
T{
\fBGE\fP
T}	T{
2 1
T}	T{
1 if A >= B, else 0
T}
_
T{
\fBGT\fP
T}	T{
2 1
T}	T{
1 if A > B, else 0
T}
_
T{
\fBHYPOT\fP
T}	T{
2 1
T}	T{
hypot (A, B) = sqrt (A*A + B*B)
T}
_
T{
\fBI0\fP
T}	T{
1 1
T}	T{
Modified Bessel function of A (1st kind, order 0)
T}
_
T{
\fBI1\fP
T}	T{
1 1
T}	T{
Modified Bessel function of A (1st kind, order 1)
T}
_
T{
\fBIFELSE\fP
T}	T{
3 1
T}	T{
B if A != 0, else C
T}
_
T{
\fBIN\fP
T}	T{
2 1
T}	T{
Modified Bessel function of A (1st kind, order B)
T}
_
T{
\fBINRANGE\fP
T}	T{
3 1
T}	T{
1 if B <= A <= C, else 0
T}
_
T{
\fBINSIDE\fP
T}	T{
1 1
T}	T{
1 when inside or on polygon(s) in A, else 0
T}
_
T{
\fBINV\fP
T}	T{
1 1
T}	T{
1 / A
T}
_
T{
\fBISFINITE\fP
T}	T{
1 1
T}	T{
1 if A is finite, else 0
T}
_
T{
\fBISNAN\fP
T}	T{
1 1
T}	T{
1 if A == NaN, else 0
T}
_
T{
\fBJ0\fP
T}	T{
1 1
T}	T{
Bessel function of A (1st kind, order 0)
T}
_
T{
\fBJ1\fP
T}	T{
1 1
T}	T{
Bessel function of A (1st kind, order 1)
T}
_
T{
\fBJN\fP
T}	T{
2 1
T}	T{
Bessel function of A (1st kind, order B)
T}
_
T{
\fBK0\fP
T}	T{
1 1
T}	T{
Modified Kelvin function of A (2nd kind, order 0)
T}
_
T{
\fBK1\fP
T}	T{
1 1
T}	T{
Modified Bessel function of A (2nd kind, order 1)
T}
_
T{
\fBKEI\fP
T}	T{
1 1
T}	T{
kei (A)
T}
_
T{
\fBKER\fP
T}	T{
1 1
T}	T{
ker (A)
T}
_
T{
\fBKM2DEG\fP
T}	T{
1 1
T}	T{
Converts Kilometers to Spherical Degrees
T}
_
T{
\fBKN\fP
T}	T{
2 1
T}	T{
Modified Bessel function of A (2nd kind, order B)
T}
_
T{
\fBKURT\fP
T}	T{
1 1
T}	T{
Kurtosis of A
T}
_
T{
\fBLCDF\fP
T}	T{
1 1
T}	T{
Laplace cumulative distribution function for z = A
T}
_
T{
\fBLCRIT\fP
T}	T{
1 1
T}	T{
Laplace distribution critical value for alpha = A
T}
_
T{
\fBLDIST\fP
T}	T{
1 1
T}	T{
Compute minimum distance (in km if \-fg) from lines in multi\-segment ASCII file A
T}
_
T{
\fBLDIST2\fP
T}	T{
2 1
T}	T{
As LDIST, from lines in ASCII file B but only to nodes where A != 0
T}
_
T{
\fBLDISTG\fP
T}	T{
0 1
T}	T{
As LDIST, but operates on the GSHHG dataset (see \-A, \-D for options).
T}
_
T{
\fBLE\fP
T}	T{
2 1
T}	T{
1 if A <= B, else 0
T}
_
T{
\fBLOG\fP
T}	T{
1 1
T}	T{
log (A) (natural log)
T}
_
T{
\fBLOG10\fP
T}	T{
1 1
T}	T{
log10 (A) (base 10)
T}
_
T{
\fBLOG1P\fP
T}	T{
1 1
T}	T{
log (1+A) (accurate for small A)
T}
_
T{
\fBLOG2\fP
T}	T{
1 1
T}	T{
log2 (A) (base 2)
T}
_
T{
\fBLMSSCL\fP
T}	T{
1 1
T}	T{
LMS scale estimate (LMS STD) of A
T}
_
T{
\fBLMSSCLW\fP
T}	T{
2 1
T}	T{
Weighted LMS scale estimate (LMS STD) of A for weights in B
T}
_
T{
\fBLOWER\fP
T}	T{
1 1
T}	T{
The lowest (minimum) value of A
T}
_
T{
\fBLPDF\fP
T}	T{
1 1
T}	T{
Laplace probability density function for z = A
T}
_
T{
\fBLRAND\fP
T}	T{
2 1
T}	T{
Laplace random noise with mean A and std. deviation B
T}
_
T{
\fBLT\fP
T}	T{
2 1
T}	T{
1 if A < B, else 0
T}
_
T{
\fBMAD\fP
T}	T{
1 1
T}	T{
Median Absolute Deviation (L1 STD) of A
T}
_
T{
\fBMAX\fP
T}	T{
2 1
T}	T{
Maximum of A and B
T}
_
T{
\fBMEAN\fP
T}	T{
1 1
T}	T{
Mean value of A
T}
_
T{
\fBMEANW\fP
T}	T{
2 1
T}	T{
Weighted mean value of A for weights in B
T}
_
T{
\fBMEDIAN\fP
T}	T{
1 1
T}	T{
Median value of A
T}
_
T{
\fBMEDIANW\fP
T}	T{
2 1
T}	T{
Weighted median value of A for weights in B
T}
_
T{
\fBMIN\fP
T}	T{
2 1
T}	T{
Minimum of A and B
T}
_
T{
\fBMOD\fP
T}	T{
2 1
T}	T{
A mod B (remainder after floored division)
T}
_
T{
\fBMODE\fP
T}	T{
1 1
T}	T{
Mode value (Least Median of Squares) of A
T}
_
T{
\fBMODEW\fP
T}	T{
2 1
T}	T{
Weighted mode value (Least Median of Squares) of A for weights in B
T}
_
T{
\fBMUL\fP
T}	T{
2 1
T}	T{
A * B
T}
_
T{
\fBNAN\fP
T}	T{
2 1
T}	T{
NaN if A == B, else A
T}
_
T{
\fBNEG\fP
T}	T{
1 1
T}	T{
\-A
T}
_
T{
\fBNEQ\fP
T}	T{
2 1
T}	T{
1 if A != B, else 0
T}
_
T{
\fBNORM\fP
T}	T{
1 1
T}	T{
Normalize (A) so max(A)\-min(A) = 1
T}
_
T{
\fBNOT\fP
T}	T{
1 1
T}	T{
NaN if A == NaN, 1 if A == 0, else 0
T}
_
T{
\fBNRAND\fP
T}	T{
2 1
T}	T{
Normal, random values with mean A and std. deviation B
T}
_
T{
\fBOR\fP
T}	T{
2 1
T}	T{
NaN if B == NaN, else A
T}
_
T{
\fBPCDF\fP
T}	T{
2 1
T}	T{
Poisson cumulative distribution function for x = A and lambda = B
T}
_
T{
\fBPDIST\fP
T}	T{
1 1
T}	T{
Compute minimum distance (in km if \-fg) from points in ASCII file A
T}
_
T{
\fBPDIST2\fP
T}	T{
2 1
T}	T{
As PDIST, from points in ASCII file B but only to nodes where A != 0
T}
_
T{
\fBPERM\fP
T}	T{
2 1
T}	T{
Permutations n_P_r, with n = A and r = B
T}
_
T{
\fBPLM\fP
T}	T{
3 1
T}	T{
Associated Legendre polynomial P(A) degree B order C
T}
_
T{
\fBPLMg\fP
T}	T{
3 1
T}	T{
Normalized associated Legendre polynomial P(A) degree B order C (geophysical convention)
T}
_
T{
\fBPOINT\fP
T}	T{
1 2
T}	T{
Compute mean x and y from ASCII file A and place them on the stack
T}
_
T{
\fBPOP\fP
T}	T{
1 0
T}	T{
Delete top element from the stack
T}
_
T{
\fBPOW\fP
T}	T{
2 1
T}	T{
A ^ B
T}
_
T{
\fBPPDF\fP
T}	T{
2 1
T}	T{
Poisson distribution P(x,lambda), with x = A and lambda = B
T}
_
T{
\fBPQUANT\fP
T}	T{
2 1
T}	T{
The B\(aqth Quantile (0\-100%) of A
T}
_
T{
\fBPQUANTW\fP
T}	T{
3 1
T}	T{
The C\(aqth weighted quantile (0\-100%) of A for weights in B
T}
_
T{
\fBPSI\fP
T}	T{
1 1
T}	T{
Psi (or Digamma) of A
T}
_
T{
\fBPV\fP
T}	T{
3 1
T}	T{
Legendre function Pv(A) of degree v = real(B) + imag(C)
T}
_
T{
\fBQV\fP
T}	T{
3 1
T}	T{
Legendre function Qv(A) of degree v = real(B) + imag(C)
T}
_
T{
\fBR2\fP
T}	T{
2 1
T}	T{
R2 = A^2 + B^2
T}
_
T{
\fBR2D\fP
T}	T{
1 1
T}	T{
Convert Radians to Degrees
T}
_
T{
\fBRAND\fP
T}	T{
2 1
T}	T{
Uniform random values between A and B
T}
_
T{
\fBRCDF\fP
T}	T{
1 1
T}	T{
Rayleigh cumulative distribution function for z = A
T}
_
T{
\fBRCRIT\fP
T}	T{
1 1
T}	T{
Rayleigh distribution critical value for alpha = A
T}
_
T{
\fBRINT\fP
T}	T{
1 1
T}	T{
rint (A) (round to integral value nearest to A)
T}
_
T{
\fBRMS\fP
T}	T{
1 1
T}	T{
Root\-mean\-square of A
T}
_
T{
\fBRMSW\fP
T}	T{
1 1
T}	T{
Root\-mean\-square of A for weights in B
T}
_
T{
\fBRPDF\fP
T}	T{
1 1
T}	T{
Rayleigh probability density function for z = A
T}
_
T{
\fBROLL\fP
T}	T{
2 0
T}	T{
Cyclicly shifts the top A stack items by an amount B
T}
_
T{
\fBROTX\fP
T}	T{
2 1
T}	T{
Rotate A by the (constant) shift B in x\-direction
T}
_
T{
\fBROTY\fP
T}	T{
2 1
T}	T{
Rotate A by the (constant) shift B in y\-direction
T}
_
T{
\fBSDIST\fP
T}	T{
2 1
T}	T{
Spherical (Great circle|geodesic) distance (in km) between nodes and stack (A, B) 
T}
_
T{
\fBSDIST2\fP
T}	T{
2 1
T}	T{
As SDIST but only to nodes that are != 0
T}
_
T{
\fBSAZ\fP
T}	T{
2 1
T}	T{
Spherical azimuth from grid nodes to stack lon, lat (i.e., A, B)
T}
_
T{
\fBSBAZ\fP
T}	T{
2 1
T}	T{
Spherical back\-azimuth from grid nodes to stack lon, lat (i.e., A, B)
T}
_
T{
\fBSEC\fP
T}	T{
1 1
T}	T{
sec (A) (A in radians)
T}
_
T{
\fBSECD\fP
T}	T{
1 1
T}	T{
sec (A) (A in degrees)
T}
_
T{
\fBSIGN\fP
T}	T{
1 1
T}	T{
sign (+1 or \-1) of A
T}
_
T{
\fBSIN\fP
T}	T{
1 1
T}	T{
sin (A) (A in radians)
T}
_
T{
\fBSINC\fP
T}	T{
1 1
T}	T{
sinc (A) (sin (pi*A)/(pi*A))
T}
_
T{
\fBSIND\fP
T}	T{
1 1
T}	T{
sin (A) (A in degrees)
T}
_
T{
\fBSINH\fP
T}	T{
1 1
T}	T{
sinh (A)
T}
_
T{
\fBSKEW\fP
T}	T{
1 1
T}	T{
Skewness of A
T}
_
T{
\fBSQR\fP
T}	T{
1 1
T}	T{
A^2
T}
_
T{
\fBSQRT\fP
T}	T{
1 1
T}	T{
sqrt (A)
T}
_
T{
\fBSTD\fP
T}	T{
1 1
T}	T{
Standard deviation of A
T}
_
T{
\fBSTDW\fP
T}	T{
2 1
T}	T{
Weighted standard deviation of A for weights in B
T}
_
T{
\fBSTEP\fP
T}	T{
1 1
T}	T{
Heaviside step function: H(A)
T}
_
T{
\fBSTEPX\fP
T}	T{
1 1
T}	T{
Heaviside step function in x: H(x\-A)
T}
_
T{
\fBSTEPY\fP
T}	T{
1 1
T}	T{
Heaviside step function in y: H(y\-A)
T}
_
T{
\fBSUB\fP
T}	T{
2 1
T}	T{
A \- B
T}
_
T{
\fBSUM\fP
T}	T{
1 1
T}	T{
Sum of all values in A
T}
_
T{
\fBTAN\fP
T}	T{
1 1
T}	T{
tan (A) (A in radians)
T}
_
T{
\fBTAND\fP
T}	T{
1 1
T}	T{
tan (A) (A in degrees)
T}
_
T{
\fBTANH\fP
T}	T{
1 1
T}	T{
tanh (A)
T}
_
T{
\fBTAPER\fP
T}	T{
2 1
T}	T{
Unit weights cosine\-tapered to zero within A and B of x and y grid margins
T}
_
T{
\fBTCDF\fP
T}	T{
2 1
T}	T{
Student\(aqs t cumulative distribution function for t = A, and nu = B
T}
_
T{
\fBTCRIT\fP
T}	T{
2 1
T}	T{
Student\(aqs t distribution critical value for alpha = A and nu = B
T}
_
T{
\fBTN\fP
T}	T{
2 1
T}	T{
Chebyshev polynomial Tn(\-1<t<+1,n), with t = A, and n = B
T}
_
T{
\fBTPDF\fP
T}	T{
2 1
T}	T{
Student\(aqs t probability density function for t = A, and nu = B
T}
_
T{
\fBTRIM\fP
T}	T{
3 1
T}	T{
Alpha\-trim C to NaN if values fall in tails A and B (in percentage)
T}
_
T{
\fBUPPER\fP
T}	T{
1 1
T}	T{
The highest (maximum) value of A
T}
_
T{
\fBVAR\fP
T}	T{
1 1
T}	T{
Variance of A
T}
_
T{
\fBVARW\fP
T}	T{
2 1
T}	T{
Weighted variance of A for weights in B
T}
_
T{
\fBWCDF\fP
T}	T{
3 1
T}	T{
Weibull cumulative distribution function for x = A, scale = B, and shape = C
T}
_
T{
\fBWCRIT\fP
T}	T{
3 1
T}	T{
Weibull distribution critical value for alpha = A, scale = B, and shape = C
T}
_
T{
\fBWPDF\fP
T}	T{
3 1
T}	T{
Weibull density distribution P(x,scale,shape), with x = A, scale = B, and shape = C
T}
_
T{
\fBWRAP\fP
T}	T{
1 1
T}	T{
wrap A in radians onto [\-pi,pi]
T}
_
T{
\fBXOR\fP
T}	T{
2 1
T}	T{
0 if A == NaN and B == NaN, NaN if B == NaN, else A
T}
_
T{
\fBY0\fP
T}	T{
1 1
T}	T{
Bessel function of A (2nd kind, order 0)
T}
_
T{
\fBY1\fP
T}	T{
1 1
T}	T{
Bessel function of A (2nd kind, order 1)
T}
_
T{
\fBYLM\fP
T}	T{
2 2
T}	T{
Re and Im orthonormalized spherical harmonics degree A order B
T}
_
T{
\fBYLMg\fP
T}	T{
2 2
T}	T{
Cos and Sin normalized spherical harmonics degree A order B (geophysical convention)
T}
_
T{
\fBYN\fP
T}	T{
2 1
T}	T{
Bessel function of A (2nd kind, order B)
T}
_
T{
\fBZCDF\fP
T}	T{
1 1
T}	T{
Normal cumulative distribution function for z = A
T}
_
T{
\fBZPDF\fP
T}	T{
1 1
T}	T{
Normal probability density function for z = A
T}
_
T{
\fBZCRIT\fP
T}	T{
1 1
T}	T{
Normal distribution critical value for alpha = A
T}
_
.TE
.SH SYMBOLS
.sp
The following symbols have special meaning:
.TS
center;
|l|l|.
_
T{
\fBPI\fP
T}	T{
3.1415926...
T}
_
T{
\fBE\fP
T}	T{
2.7182818...
T}
_
T{
\fBEULER\fP
T}	T{
0.5772156...
T}
_
T{
\fBEPS_F\fP
T}	T{
1.192092896e\-07 (single precision epsilon
T}
_
T{
\fBXMIN\fP
T}	T{
Minimum x value
T}
_
T{
\fBXMAX\fP
T}	T{
Maximum x value
T}
_
T{
\fBXRANGE\fP
T}	T{
Range of x values
T}
_
T{
\fBXINC\fP
T}	T{
x increment
T}
_
T{
\fBNX\fP
T}	T{
The number of x nodes
T}
_
T{
\fBYMIN\fP
T}	T{
Minimum y value
T}
_
T{
\fBYMAX\fP
T}	T{
Maximum y value
T}
_
T{
\fBYRANGE\fP
T}	T{
Range of y values
T}
_
T{
\fBYINC\fP
T}	T{
y increment
T}
_
T{
\fBNY\fP
T}	T{
The number of y nodes
T}
_
T{
\fBX\fP
T}	T{
Grid with x\-coordinates
T}
_
T{
\fBY\fP
T}	T{
Grid with y\-coordinates
T}
_
T{
\fBXNORM\fP
T}	T{
Grid with normalized [\-1 to +1] x\-coordinates
T}
_
T{
\fBYNORM\fP
T}	T{
Grid with normalized [\-1 to +1] y\-coordinates
T}
_
T{
\fBXCOL\fP
T}	T{
Grid with column numbers 0, 1, ..., NX\-1
T}
_
T{
\fBYROW\fP
T}	T{
Grid with row numbers 0, 1, ..., NY\-1
T}
_
T{
\fBNODE\fP
T}	T{
Grid with node numbers 0, 1, ..., (NX*NY)\-1
T}
_
.TE
.SH NOTES ON OPERATORS
.INDENT 0.0
.IP 1. 4
For Cartesian grids the operators \fBMEAN\fP, \fBMEDIAN\fP, \fBMODE\fP,
\fBLMSSCL\fP, \fBMAD\fP, \fBPQUANT\fP, \fBRMS\fP, \fBSTD\fP, and \fBVAR\fP return the
expected value from the given matrix.  However, for geographic grids
we perform a spherically weighted calculation where each node value
is weighted by the geographic area represented by that node.
.IP 2. 4
The operator \fBSDIST\fP calculates spherical distances in km between the
(lon, lat) point on the stack and all node positions in the grid. The
grid domain and the (lon, lat) point are expected to be in degrees.
Similarly, the \fBSAZ\fP and \fBSBAZ\fP operators calculate spherical
azimuth and back\-azimuths in degrees, respectively. The operators
\fBLDIST\fP and \fBPDIST\fP compute spherical distances in km if \fB\-fg\fP is
set or implied, else they return Cartesian distances. Note: If the current
PROJ_ELLIPSOID is ellipsoidal then
geodesics are used in calculations of distances, which can be slow.
You can trade speed with accuracy by changing the algorithm used to
compute the geodesic (see PROJ_GEODESIC).
.sp
The operator \fBLDISTG\fP is a version of \fBLDIST\fP that operates on the
GSHHG data. Instead of reading an ASCII file, it directly accesses one of
the GSHHG data sets as determined by the \fB\-D\fP and \fB\-A\fP options.
.IP 3. 4
The operator \fBPOINT\fP reads a ASCII table, computes the mean x and mean
y values and places these on the stack.  If geographic data then we use
the mean 3\-D vector to determine the mean location.
.IP 4. 4
The operator \fBPLM\fP calculates the associated Legendre polynomial
of degree L and order M (0 <= M <= L), and its argument is the sine of
the latitude. \fBPLM\fP is not normalized and includes the Condon\-Shortley
phase (\-1)^M. \fBPLMg\fP is normalized in the way that is most commonly
used in geophysics. The C\-S phase can be added by using \-M as argument.
\fBPLM\fP will overflow at higher degrees, whereas \fBPLMg\fP is stable
until ultra high degrees (at least 3000).
.IP 5. 4
The operators \fBYLM\fP and \fBYLMg\fP calculate normalized spherical
harmonics for degree L and order M (0 <= M <= L) for all positions in
the grid, which is assumed to be in degrees. \fBYLM\fP and \fBYLMg\fP return
two grids, the real (cosine) and imaginary (sine) component of the
complex spherical harmonic. Use the \fBPOP\fP operator (and \fBEXCH\fP) to
get rid of one of them, or save both by giving two consecutive = file.nc calls.
.sp
The orthonormalized complex harmonics \fBYLM\fP are most commonly used in
physics and seismology. The square of \fBYLM\fP integrates to 1 over a
sphere. In geophysics, \fBYLMg\fP is normalized to produce unit power when
averaging the cosine and sine terms (separately!) over a sphere (i.e.,
their squares each integrate to 4 pi). The Condon\-Shortley phase (\-1)^M
is not included in \fBYLM\fP or \fBYLMg\fP, but it can be added by using \-M
as argument.
.IP 6. 4
All the derivatives are based on central finite differences, with
natural boundary conditions, and are Cartesian derivatives.
.IP 7. 4
Files that have the same names as some operators, e.g., \fBADD\fP,
\fBSIGN\fP, \fB=\fP, etc. should be identified by prepending the current
directory (i.e., ./LOG).
.IP 8. 4
Piping of files is not allowed.
.IP 9. 4
The stack depth limit is hard\-wired to 100.
.IP 10. 4
All functions expecting a positive radius (e.g., \fBLOG\fP, \fBKEI\fP,
etc.) are passed the absolute value of their argument. (9) The bitwise
operators (\fBBITAND\fP, \fBBITLEFT\fP, \fBBITNOT\fP, \fBBITOR\fP, \fBBITRIGHT\fP,
\fBBITTEST\fP, and \fBBITXOR\fP) convert a grid\(aqs single precision values to
unsigned 32\-bit ints to perform the bitwise operations. Consequently,
the largest whole integer value that can be stored in a float grid is
2^24 or 16,777,216. Any higher result will be masked to fit in the lower
24 bits.  Thus, bit operations are effectively limited to 24 bit.  All
bitwise operators return NaN if given NaN arguments or bit\-settings <= 0.
.IP 11. 4
When OpenMP support is compiled in, a few operators will take advantage
of the ability to spread the load onto several cores.  At present, the
list of such operators is: \fBLDIST\fP, \fBLDIST2\fP, \fBPDIST\fP, \fBPDIST2\fP,
\fBSAZ\fP, \fBSBAZ\fP, \fBSDIST\fP, \fBYLM\fP, and \fBgrd_YLMg\fP\&.
.UNINDENT
.SH GRID VALUES PRECISION
.sp
Regardless of the precision of the input data, GMT programs that create
grid files will internally hold the grids in 4\-byte floating point
arrays. This is done to conserve memory and furthermore most if not all
real data can be stored using 4\-byte floating point values. Data with
higher precision (i.e., double precision values) will lose that
precision once GMT operates on the grid or writes out new grids. To
limit loss of precision when processing data you should always consider
normalizing the data prior to processing.
.SH GRID FILE FORMATS
.sp
By default GMT writes out grid as single precision floats in a
COARDS\-complaint netCDF file format. However, GMT is able to produce
grid files in many other commonly used grid file formats and also
facilitates so called "packing" of grids, writing out floating point
data as 1\- or 2\-byte integers. (more ...)
.SH GEOGRAPHICAL AND TIME COORDINATES
.sp
When the output grid type is netCDF, the coordinates will be labeled
"longitude", "latitude", or "time" based on the attributes of the input
data or grid (if any) or on the \fB\-f\fP or \fB\-R\fP options. For example,
both \fB\-f0x\fP \fB\-f1t\fP and \fB\-R\fP90w/90e/0t/3t will result in a
longitude/time grid. When the x, y, or z coordinate is time, it will be
stored in the grid as relative time since epoch as specified by
TIME_UNIT and TIME_EPOCH in the
gmt.conf file or on the
command line. In addition, the \fBunit\fP attribute of the time variable
will indicate both this unit and epoch.
.SH STORE, RECALL AND CLEAR
.sp
You may store intermediate calculations to a named variable that you may
recall and place on the stack at a later time. This is useful if you
need access to a computed quantity many times in your expression as it
will shorten the overall expression and improve readability. To save a
result you use the special operator \fBSTO\fP@\fIlabel\fP, where \fIlabel\fP
is the name you choose to give the quantity. To recall the stored result
to the stack at a later time, use [\fBRCL\fP]@\fIlabel\fP, i.e., \fBRCL\fP
is optional. To clear memory you may use \fBCLR\fP@\fIlabel\fP\&. Note that
\fBSTO\fP and \fBCLR\fP leave the stack unchanged.
.SH GSHHS INFORMATION
.sp
The coastline database is GSHHG (formerly GSHHS) which is compiled from
three sources:  World Vector Shorelines (WVS), CIA World Data Bank II
(WDBII), and Atlas of the Cryosphere (AC, for Antarctica only).
Apart from Antarctica, all level\-1 polygons (ocean\-land boundary) are derived from
the more accurate WVS while all higher level polygons (level 2\-4,
representing land/lake, lake/island\-in\-lake, and
island\-in\-lake/lake\-in\-island\-in\-lake boundaries) are taken from WDBII.
The Antarctica coastlines come in two flavors: ice\-front or grounding line,
selectable via the \fB\-A\fP option.
Much processing has taken place to convert WVS, WDBII, and AC data into
usable form for GMT: assembling closed polygons from line segments,
checking for duplicates, and correcting for crossings between polygons.
The area of each polygon has been determined so that the user may choose
not to draw features smaller than a minimum area (see \fB\-A\fP); one may
also limit the highest hierarchical level of polygons to be included (4
is the maximum). The 4 lower\-resolution databases were derived from the
full resolution database using the Douglas\-Peucker line\-simplification
algorithm. The classification of rivers and borders follow that of the
WDBII. See the GMT Cookbook and Technical Reference Appendix K for
further details.
.SH MACROS
.sp
Users may save their favorite operator combinations as macros via the
file \fIgrdmath.macros\fP in their current or user directory. The file may contain
any number of macros (one per record); comment lines starting with # are
skipped. The format for the macros is \fBname\fP = \fBarg1 arg2 ... arg2\fP
: \fIcomment\fP where \fBname\fP is how the macro will be used. When this
operator appears on the command line we simply replace it with the
listed argument list. No macro may call another macro. As an example,
the following macro expects three arguments (radius x0 y0) and sets the
modes that are inside the given circle to 1 and those outside to 0:
.sp
INCIRCLE = CDIST EXCH DIV 1 LE : usage: r x y INCIRCLE to return 1
inside circle
.sp
Note: Because geographic or time constants may be present in a macro, it
is required that the optional comment flag (:) must be followed by a space.
.SH EXAMPLES
.sp
To compute all distances to north pole:
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
gmt grdmath \-Rg \-I1 0 90 SDIST = dist_to_NP.nc
.ft P
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.UNINDENT
.sp
To take log10 of the average of 2 files, use
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
gmt grdmath file1.nc file2.nc ADD 0.5 MUL LOG10 = file3.nc
.ft P
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.UNINDENT
.sp
Given the file ages.nc, which holds seafloor ages in m.y., use the
relation depth(in m) = 2500 + 350 * sqrt (age) to estimate normal seafloor depths:
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
gmt grdmath ages.nc SQRT 350 MUL 2500 ADD = depths.nc
.ft P
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.UNINDENT
.sp
To find the angle a (in degrees) of the largest principal stress from
the stress tensor given by the three files s_xx.nc s_yy.nc, and
s_xy.nc from the relation tan (2*a) = 2 * s_xy / (s_xx \- s_yy), use
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
gmt grdmath 2 s_xy.nc MUL s_xx.nc s_yy.nc SUB DIV ATAN 2 DIV = direction.nc
.ft P
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.UNINDENT
.sp
To calculate the fully normalized spherical harmonic of degree 8 and
order 4 on a 1 by 1 degree world map, using the real amplitude 0.4 and
the imaginary amplitude 1.1:
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
gmt grdmath \-R0/360/\-90/90 \-I1 8 4 YLM 1.1 MUL EXCH 0.4 MUL ADD = harm.nc
.ft P
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.UNINDENT
.sp
To extract the locations of local maxima that exceed 100 mGal in the file faa.nc:
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
gmt grdmath faa.nc DUP EXTREMA 2 EQ MUL DUP 100 GT MUL 0 NAN = z.nc
gmt grd2xyz z.nc \-s > max.xyz
.ft P
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.UNINDENT
.sp
To demonstrate the use of named variables, consider this radial wave
where we store and recall the normalized radial arguments in radians:
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
gmt grdmath \-R0/10/0/10 \-I0.25 5 5 CDIST 2 MUL PI MUL 5 DIV STO@r COS @r SIN MUL = wave.nc
.ft P
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.UNINDENT
.sp
To creat a dumb file saved as a 32 bits float GeoTiff using GDAL, run
.INDENT 0.0
.INDENT 3.5
.INDENT 0.0
.INDENT 3.5
.sp
.nf
.ft C
gmt grdmath \-Rd \-I10 X Y MUL = lixo.tiff=gd:GTiff
.ft P
.fi
.UNINDENT
.UNINDENT
.UNINDENT
.UNINDENT
.SH REFERENCES
.sp
Abramowitz, M., and I. A. Stegun, 1964, \fIHandbook of Mathematical
Functions\fP, Applied Mathematics Series, vol. 55, Dover, New York.
.sp
Holmes, S. A., and W. E. Featherstone, 2002, A unified approach to the
Clenshaw summation and the recursive computation of very high degree and
order normalised associated Legendre functions. \fIJournal of Geodesy\fP,
76, 279\-299.
.sp
Press, W. H., S. A. Teukolsky, W. T. Vetterling, and B. P. Flannery,
1992, \fINumerical Recipes\fP, 2nd edition, Cambridge Univ., New York.
.sp
Spanier, J., and K. B. Oldman, 1987, \fIAn Atlas of Functions\fP, Hemisphere
Publishing Corp.
.SH SEE ALSO
.sp
gmt, gmtmath,
grd2xyz, grdedit,
grdinfo, xyz2grd
.SH COPYRIGHT
2019, P. Wessel, W. H. F. Smith, R. Scharroo, J. Luis, and F. Wobbe
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