mkfunc -- Make a file containing functional form data and proper FITS coordinates.
mkfunc output function npts shift
This task lets the user specify a function name (the same functions as used in the testfunc task), a number of data points, and the origin offset from the first pixel. From this a file is built that contains data from the function.
- output [file]
- Name of output image.
- function [string]
- [Allowed values: bessel | constant | delta | gaussian |
heaviside | pe | po | box | rectangle | signum | comb |
shah | sinc | sine | cosine | triangle | y | line]
Name of the function to be used. The following table shows the supported functions, which are described in Bracewell's book "The Fourier Transform and Its Applications."
Value Function ===== ======== bessel Bessel function ('J0') box Bracewell's box function comb Dirac comb, Bracewell shah constant Constant cosine cosine delta Delta function gaussian Gaussian heaviside Heaviside unit step line Unit-slope line pe Even impulse pair po Odd impulse pair rectangle Bracewell's box function shah Dirac comb, Bracewell shah signum sign (x) sinc sin (pi x) / (pi x) sine sine triangle Bracewell's wedge function y Unit-slope line
- npts = [integer, min=1]
- Number of points.
- shift = [integer]
- Shift origin (in pixels).
- (constant = 1.0) [real]
- Value of the constant function.
- (fcw = 10.0) [real, min=1.0]
- Characteristic width of the function.
The bold and inquisitive user may also adjust the "characteristic width" of the function, which may have different meanings for different functions. For things like the boxcar or Gaussian functions, the notion of width is pretty intuitive; for things like the impulse pairs function, it represents the separation of the pulses. "Characteristic width" is meaningless for things like a delta function or a step function.
1. Use mkfunc to create a file called cos.hhh. Use the cosine function with 100 data points.
fo> mkfunc cos.hhh cosine 100 0
Type "help fourier option=sys" for a higher-level description of the fourier package.