## table of contents

- bullseye 1:2.025-1
- testing 1:2.080-3+b1
- unstable 1:2.081-1
- experimental 1:2.081-1~exp1

Complex(3pm) | User Contributed Perl Documentation | Complex(3pm) |

# NAME¶

PDL::Complex - handle complex numbers (DEPRECATED - use native complex)

# SYNOPSIS¶

use PDL; use PDL::Complex;

# DESCRIPTION¶

This module is deprecated in favour of using "native complex" data types, e.g.:

use PDL; my $complex_pdl = cdouble('[1+3i]'); print $complex_pdl * pdl('i'); # [-3+i]

This module features a growing number of functions manipulating complex numbers. These are usually represented as a pair "[ real imag ]" or "[ magnitude phase ]". If not explicitly mentioned, the functions can work inplace (not yet implemented!!!) and require rectangular form.

While there is a procedural interface available ("$x/$y*$c <=> Cmul (Cdiv ($x, $y), $c)"), you can also opt to cast your pdl's into the "PDL::Complex" datatype, which works just like your normal ndarrays, but with all the normal perl operators overloaded.

The latter means that "sin($x) + $y/$c" will be evaluated using the normal rules of complex numbers, while other pdl functions (like "max") just treat the ndarray as a real-valued ndarray with a lowest dimension of size 2, so "max" will return the maximum of all real and imaginary parts, not the "highest" (for some definition)

## Native complex support¶

2.027 added changes in complex number handling, with support for C99 complex floating-point types, and most functions and modules in the core distribution support these as well.

PDL can now handle complex numbers natively as scalars. This has the advantage that real and complex valued ndarrays have the same dimensions. Consider this when writing code in the future.

See "re" in PDL::Ops, "im" in PDL::Ops, "abs" in PDL::Ops, "carg" in PDL::Ops, "conj" in PDL::Ops for more.

# TIPS, TRICKS & CAVEATS¶

- "i" is a function (not, as of 2.047, a
constant) exported by this module, which represents
"-1**0.5", i.e. the imaginary unit. it
can be used to quickly and conveniently write complex constants like this:
"4+3*i".
**NB**This will override the PDL::Core function of the same name, which returns a native complex value. - Use "r2C(real-values)" to convert from real to complex, as in "$r = Cpow $cplx, r2C 2". The overloaded operators automatically do that for you, all the other functions, do not. So "Croots 1, 5" will return all the fifths roots of 1+1*i (due to broadcasting).
- use "cplx(real-valued-ndarray)" to cast from normal ndarrays into the complex datatype. Use "real(complex-valued-ndarray)" to cast back. This requires a copy, though.

# EXAMPLE WALK-THROUGH¶

The complex constant five is equal to "pdl(1,0)":

pdl> p $x = r2C 5 5 +0i

Now calculate the three cubic roots of five:

pdl> p $r = Croots $x, 3 [1.70998 +0i -0.854988 +1.48088i -0.854988 -1.48088i]

Check that these really are the roots:

pdl> p $r ** 3 [5 +0i 5 -1.22465e-15i 5 -7.65714e-15i]

Duh! Could be better. Now try by multiplying $r three times with itself:

pdl> p $r*$r*$r [5 +0i 5 -4.72647e-15i 5 -7.53694e-15i]

Well... maybe "Cpow" (which is used by the "**" operator) isn't as bad as I thought. Now multiply by "i" and negate, then take the complex conjugate, which is just a very expensive way of swapping real and imaginary parts.

pdl> p Cconj(-($r*i)) [0 +1.70998i 1.48088 -0.854988i -1.48088 -0.854988i]

Now plot the magnitude of (part of) the complex sine. First generate the coefficients:

pdl> $sin = i * zeroes(50)->xlinvals(2,4) + zeroes(50)->xlinvals(0,7)

Now plot the imaginary part, the real part and the magnitude of the sine into the same diagram:

pdl> use PDL::Graphics::Gnuplot pdl> gplot( with => 'lines', PDL::cat(im ( sin $sin ), re ( sin $sin ), abs( sin $sin ) ))

An ASCII version of this plot looks like this:

30 ++-----+------+------+------+------+------+------+------+------+-----++ + + + + + + + + + + + | $$| | $ | 25 ++ $$ ++ | *** | | ** *** | | $$* *| 20 ++ $** ++ | $$$* #| | $$$ * # | | $$ * # | 15 ++ $$$ * # ++ | $$$ ** # | | $$$$ * # | | $$$$ * # | 10 ++ $$$$$ * # ++ | $$$$$ * # | | $$$$$$$ * # | 5 ++ $$$############ * # ++ |*****$$$### ### * # | * #***** # * # | | ### *** ### ** # | 0 ## *** # * # ++ | * # * # | | *** # ** # | | * # * # | -5 ++ ** # * # ++ | *** ## ** # | | * #* # | | **** ***## # | -10 ++ **** # # ++ | # # | | ## ## | + + + + + + + ### + ### + + + -15 ++-----+------+------+------+------+------+-----###-----+------+-----++ 0 5 10 15 20 25 30 35 40 45 50

# OPERATORS¶

The following operators are overloaded:

- +, += (addition)
- -, -= (subtraction)
- *, *= (multiplication; "Cmul")
- /, /= (division; "Cdiv")
- **, **= (exponentiation; "Cpow")
- atan2 (4-quadrant arc tangent)
- sin ("Csin")
- cos ("Ccos")
- exp ("Cexp")
- abs ("Cabs")
- log ("Clog")
- sqrt ("Csqrt")
- ++, -- (increment, decrement; they affect the real part of the complex number only)
- "" (stringification)

Comparing complex numbers other than for equality is a fatal error.

# FUNCTIONS¶

## from_native¶

Class method to convert a native-complex ndarray to a PDL::Complex object.

PDL::Complex->from_native($native_complex_ndarray)

## as_native¶

Object method to convert a PDL::Complex object to a native-complex ndarray.

$pdl_complex_obj->as_native

## cplx¶

Cast a real-valued ndarray to the complex datatype.

The first dimension of the ndarray must be of size 2. After this the usual (complex) arithmetic operators are applied to this pdl, rather than the normal elementwise pdl operators. Dataflow to the complex parent works. Use "sever" on the result if you don't want this.

cplx($real_valued_pdl)

## complex¶

Cast a real-valued ndarray to the complex datatype *without*
dataflow and *inplace*.

Achieved by merely reblessing an ndarray. The first dimension of the ndarray must be of size 2.

complex($real_valued_pdl)

## real¶

Cast a complex valued pdl back to the "normal" pdl datatype.

Afterwards the normal elementwise pdl operators are used in operations. Dataflow to the real parent works. Use "sever" on the result if you don't want this.

real($cplx_valued_pdl)

## r2C¶

Signature: (r(); [o]c(m=2))

convert real to complex, assuming an imaginary part of zero

r2C does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## i2C¶

Signature: (r(); [o]c(m=2))

convert imaginary to complex, assuming a real part of zero

i2C does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Cr2p¶

Signature: (r(m=2); float+ [o]p(m=2))

convert complex numbers in rectangular form to polar (mod,arg) form. Works inplace

Cr2p does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Cp2r¶

Signature: (r(m=2); [o]p(m=2))

convert complex numbers in polar (mod,arg) form to rectangular form. Works inplace

Cp2r does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Cmul¶

Signature: (a(m=2); b(m=2); [o]c(m=2))

complex multiplication

Cmul does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Cprodover¶

Signature: (a(m=2,n); [o]c(m=2))

Project via product to N-1 dimension

Cprodover does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Cscale¶

Signature: (a(m=2); b(); [o]c(m=2))

mixed complex/real multiplication

Cscale does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Cdiv¶

Signature: (a(m=2); b(m=2); [o]c(m=2))

complex division

Cdiv does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Ceq¶

Signature: (a(m=2); b(m=2); [o]c())

Complex equality operator.

Ceq does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Cconj¶

Signature: (a(m=2); [o]c(m=2))

complex conjugation. Works inplace

Cconj does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Cabs¶

Signature: (a(m=2); [o]c())

complex "abs()" (also known as
*modulus*)

Cabs does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Cabs2¶

Signature: (a(m=2); [o]c())

complex squared "abs()" (also
known *squared modulus*)

Cabs2 does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Carg¶

Signature: (a(m=2); [o]c())

complex argument function ("angle")

Carg does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Csin¶

Signature: (a(m=2); [o]c(m=2))

sin (a) = 1/(2*i) * (exp (a*i) - exp (-a*i)). Works inplace

Csin does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Ccos¶

Signature: (a(m=2); [o]c(m=2))

cos (a) = 1/2 * (exp (a*i) + exp (-a*i)). Works inplace

Ccos does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Ctan¶

Complex tangent

tan (a) = -i * (exp (a*i) - exp (-a*i)) / (exp (a*i) + exp (-a*i))

Does not work inplace.

## Cexp¶

Signature: (a(m=2); [o]c(m=2))

exp (a) = exp (real (a)) * (cos (imag (a)) + i * sin (imag (a))). Works inplace

Cexp does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Clog¶

Signature: (a(m=2); [o]c(m=2))

log (a) = log (cabs (a)) + i * carg (a). Works inplace

Clog does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Cpow¶

Signature: (a(m=2); b(m=2); [o]c(m=2))

complex "pow()" ("**"-operator)

Cpow does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Csqrt¶

Signature: (a(m=2); [o]c(m=2))

Works inplace

Csqrt does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Casin¶

Signature: (a(m=2); [o]c(m=2))

Works inplace

Casin does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Cacos¶

Signature: (a(m=2); [o]c(m=2))

Works inplace

Cacos does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Catan¶

Return the complex "atan()".

Does not work inplace.

## Csinh¶

Signature: (a(m=2); [o]c(m=2))

sinh (a) = (exp (a) - exp (-a)) / 2. Works inplace

Csinh does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Ccosh¶

Signature: (a(m=2); [o]c(m=2))

cosh (a) = (exp (a) + exp (-a)) / 2. Works inplace

Ccosh does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Ctanh¶

Signature: (a(m=2); [o]c(m=2))

Works inplace

Ctanh does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Casinh¶

Signature: (a(m=2); [o]c(m=2))

Works inplace

Casinh does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Cacosh¶

Signature: (a(m=2); [o]c(m=2))

Works inplace

Cacosh does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Catanh¶

Signature: (a(m=2); [o]c(m=2))

Works inplace

Catanh does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Cproj¶

Signature: (a(m=2); [o]c(m=2))

compute the projection of a complex number to the riemann sphere. Works inplace

Cproj does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## Croots¶

Signature: (a(m=2); [o]c(m=2,n); int n => n)

Compute the "n" roots of "a". "n" must be a positive integer. The result will always be a complex type!

Croots does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

## re, im¶

Return the real or imaginary part of the complex number(s) given.

These are slicing operators, so data flow works. The real and imaginary parts are returned as ndarrays (ref eq PDL).

## rCpolynomial¶

Signature: (coeffs(n); x(c=2,m); [o]out(c=2,m))

evaluate the polynomial with (real) coefficients "coeffs" at the (complex) position(s) "x". "coeffs[0]" is the constant term.

rCpolynomial does not process bad values. It will set the bad-value flag of all output ndarrays if the flag is set for any of the input ndarrays.

# AUTHOR¶

Copyright (C) 2000 Marc Lehmann <pcg@goof.com>. All rights reserved. There is no warranty. You are allowed to redistribute this software / documentation as described in the file COPYING in the PDL distribution.

# SEE ALSO¶

**perl**(1), PDL.

2022-10-26 | perl v5.36.0 |