Example: Converting ASCII to raw¶

You have a whole slew of data files in ASCII from an experiment that you ran in your lab. You're still tweaking the analysis and plots, so you'd like if your data could load as fast as possible. Eventually you'll read the data into your scripts using "readfraw", but the first thing you might do is create a script that converts all the data files to raw files:

 #!/usr/bin/perl
 # Assumes that the data files end with a .asc or .dat extension
 # and saves the raw file output with a .bdat extension.
 # call with
 #  >./convert_to_raw.pl file1.dat file2.dat ...
 # or
 #  >./convert_to_raw.pl *.dat
 
 use PDL;
 use PDL::IO::FastRaw;  # for saving raw files
 use PDL::IO::Misc;             # for reading ASCII files with rcols
 while(shift) {                 # run through the entire supplied list of file names
         ($newName = $_) =~ s/\.(asc|dat)/.bdat/;
         print "Saving contents of $_ to $newName\n";
         $data = rcols($_);
         writefraw($data, $newName);
 }

Example: readfraw¶

Now that you've gotten your data into a raw file format, you can start working on your analysis scripts. If you scripts used "rcols" in the past, the reading portion of the script should go much, much faster now:

 #!/usr/bin/perl
 # My plotting script.
 # Assume I've specified the files to plot on the command line like
 #  >./plot_script.pl file1.bdat file2.bdat ...
 # or
 #  >./plot_script.pl *.bdat
 
 use PDL;
 use PDL::IO::FastRaw;
 while(shift) {                 # run through the entire supplied list of file names
         $data = readfraw($_);
         my_plot_func($data);
 }

Example: Custom headers¶

In the first example, I allow "writefraw" to use the standard header file name, which would be "file.bdat.hdr". However, I often measure time series that have identical length, so all of those header files are redundant. To fix that, I simply pass the Header option to the "writefraw" command. A modified script would look like this:

 #!/usr/bin/perl
 # Assumes that the data files end with a .asc or .dat extension
 # and saves the raw file output with a .bdat extension.
 # call with
 #  >./convert_to_raw.pl [-hHeaderFile] <fileglob> [-hHeaderFile] <fileglob> ...
 
 use PDL;
 use PDL::IO::FastRaw;  # for saving raw files
 use PDL::IO::Misc;             # for reading ASCII files with rcols
 my $header_file = undef;
 CL_OPTION: while($_ = shift @ARGV) {   # run through the entire list of command-line options
         if(/-h(.*)/) {
                 $header_file = $1;
                 next CL_OPTION;
         }
         ($newName = $_) =~ s/\.(asc|dat)/.bdat/;
         print "Saving contents of $_ to $newName\n";
         $data = rcols($_);
         writefraw($data, $newName, {Header => $header_file});
 }

Modifying the read script is left as an exercise for the reader. :]

Example: Using mapfraw¶

Sometimes you'll want to use "mapfraw" rather than the read/write functions. In fact, the original author of the module doesn't use the read/write functions anymore, prefering to always use "mapfraw". How would you go about doing this?

Assuming you've already saved your data into the raw format, the only change you would have to make to the script in example 2 would be to change the call to "readfraw" to "mapfraw". That's it. You will probably see differences in performance, though I (David Mertens) couldn't tell you about them because I haven't played around with "mapfraw" much myself.

What if you eschew the use of "writefraw" and prefer to only use "mapfraw"? How would you save your data to a raw format? In that case, you would have to create a "mapfraw" ndarray with the correct dimensions first using

 $ndarray_on_hd = mapfraw('fname', {Creat => 1, Dims => [dim1, dim2, ...]});

Note that you must specify the dimensions and you must tell "mapfraw" to create the new ndarray for you by setting the "Creat" option to a true value, not "Create" (note the missing final 'e').

writefraw¶

Write a raw format binary file

 writefraw($pdl,"fname");
 writefraw($pdl,"fname", {Header => 'headerfname'});

The "writefraw" command supports the following option:

Header

Specify the header file name.

readfraw¶

Read a raw format binary file

 $pdl2 = readfraw("fname");
 $pdl2 = PDL->readfraw("fname");
 $pdl2 = readfraw("fname", {Header => 'headerfname'});

The "readfraw" command supports the following option:

Header

Specify the header file name.

gluefraw¶

Append a single data item to an existing binary file written by "writefraw". Error if dims not compatible with existing data.

  gluefraw($file, $pdl[, $opts]);

mapfraw¶

Memory map a raw format binary file (see the module docs also)

 $pdl3 = mapfraw("fname2",{ReadOnly => 1});

The "mapfraw" command supports the following options (not all combinations make sense):

Dims, Datatype

If creating a new file or if you want to specify your own header data for the file, you can give an array reference and a scalar, respectively.

Creat

Create the file. Also writes out a header for the file.

Trunc

Set the file size. Automatically enabled with "Creat". NOTE: This also clears the file to all zeroes.

ReadOnly

Disallow writing to the file.

Header

Specify the header file name.

maptextfraw¶

Memory map a text file (see the module docs also).

Note that this function maps the raw format so if you are using an operating system which does strange things to e.g. line delimiters upon reading a text file, you get the raw (binary) representation.

The file doesn't really need to be text but it is just mapped as one large binary chunk.

This function is just a convenience wrapper which firsts "stat"s the file and sets the dimensions and datatype.

 $pdl4 = maptextfraw("fname", {options}

The options other than Dims, Datatype of "mapfraw" are supported.