— Command: output-file n

This command sets the name of the output file to n. If n is the false value #f, gmeteor produces no output. If n is the string "-", gmeteor outputs to standard output. The default value is "-".

The output file contains the filter coefficients, and additional information when the verbose mode is on.

— Command: plot-file n

This command sets the name of the plot file to n. If n is the false value #f, gmeteor produces no plot file. If n is the string "-", gmeteor outputs the plot file to standard output. The default value is #f.

The plot file contains a series of lines of the form f H(f), for various frequencies f equispaced between 0 and half the sampling frequency. The spacing is controlled by the plot grid density parameter.

— Command: plot-absolute b

If b is the true value #t, then gmeteor plots the absolute value of the frequency response in the plot file. The default is to plot the signed value, which corresponds to (plot-absolute #f).

— Command: verbose b

If b is the true value #t, then gmeteor prints the design parameters to the output file, in addition to the filter coefficients. The default is not to print additional information, which corresponds to (verbose #f).

The additional information includes the title, symmetry, filter length, grid density, and the list of specifications.

— Command: grid-density n

Set the grid density for the filter. gmeteor samples all frequencies on a finite grid consisting of n frequencies between 0 and half the sampling frequencies. If unspecified, the grid density is about ten times the filter length.

— Command: plot-grid-density n

Set the plot grid density for the filter. For the purposes of producing a plot file, gmeteor samples all frequencies on a finite grid consisting of n frequencies between 0 and half the sampling frequencies. If unspecified, the plot grid density equals the grid density.

— Command: go

Compute the optimal filter and print the output files. gmeteor does not compute anything unless this command is given.

The rationale for an explicit (go) command is that you may want to perform some processing after the filter has been computed. For example, you may want to output the filter coefficients using your own routine written in Scheme. Without (go), gmeteor would not know whether you are still specifying the filter or whether you need to know the result.