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##

Structure: `struct struct_tfparam`

The structure `struct_tfparam` is the main structure used by the
time-frequency routines and the program calling these routines. Some
of the fields of this structure are used by the time-frequency
routines while others are others are useful for book keeping.
(We will use the abbreviation BK to denote the fields used for Book Keeping.)
The fields of this structure are:

`struct_tfparam{`

`int run_number`: BK. An identification label.
`float f_lower`: BK. The lower frequency cutoff for the
signals injected.
`int start_segment`: BK. Used by the calling program to
identfy the first data segment to analyse.
`int transformtype`: The type of the time-frequency
transform to be used to construct the map. Should be set to any one of
the three Macros defined in file grasp.h, namely, WIGNERTF,
WIGNERTF_NP, WFFTWTF,
or CHOIWILLIAMS which correspond to the
currently implemented transforms namely,the Wigner-Ville transform
with zero padding, Wigner-Ville transform without zero padding,
the windowed Fourier transform and the Choi-Williams transform
respectively.
`int windowidth`: The width (in number of data points)
of the window to use for the Choi-Williams and the windowed Fourier transform.
`int offset_step_size`:
This variable governs the resolution at which the TF map is computed
and should normally be
set to unity. If this variable is not set to unity then the
TF distributions are not computed for every value of time. For
example if this variable is set to 2 then the TF
distribution is computed at half the resolution.
`int num_of_segments`: BK. The number of data segments to analyse.
`float maxpixelval`: Can be used to set a threshhold on
the values of the pixels in the TF map. This value can be
computed using the routine `compute_scalefactor()`.
`int DIM`: The data dimension of the data segment array.
`int ND`: The data dimension of the subsegment array.
`int PD`: The dimension of the TF map. Must be less that
ND/4.
`int PRE`: The number of data points to skip at the beginning
of each segment.
`int POST`: The number of data points to skip at the end
of each segment.
`int TD`: Has to be set to ND/PD.
`int FD`: Has to be set to ND/(4*PD)
`float rescale_factor`: Used to compute maxpixelval via the routine
`compute_scale_factor()`. Has to be set to a number
greater than unity.
`float hscale`: BK. An arbitrary scaling number.
`int noisetype`: BK. The type of noise.
`float srate`: The sampling rate.

`}`

** Next:** Function: time_freq_map()
** Up:** GRASP Routines: Time-Frequency Methods
** Previous:** Steger's Line Detection Routines
** Contents**
Bruce Allen
2000-11-19