Because not all all items with selfdocs are executable, an additional mechanism is necessary to see the selfdoc for these items. For example, information about the Abel transform routines, located in $CWPROOT/src/cwp/lib/abel.c (on the system at CWP, CWPROOT=/usr/local/cwp) is obtained via
% sudoc abel In /usr/local/cwp/src/cwp/lib: ABEL - Functions to compute the discrete ABEL transform: abelalloc allocate and return a pointer to an Abel transformer abelfree free an Abel transformer abel compute the Abel transform Function prototypes: void *abelalloc (int n); void abelfree (void *at); void abel (void *at, float f, float g); Input: ns number of samples in the data to be transformed f array of floats, the function being transformed Output: at pointer to Abel transformer returned by abelalloc(int n) g array of floats, the transformed data returned by abel(*at,f,g) Notes: The Abel transform is defined by: Infinity g(y) = 2 Integral dx f(x)/sqrt(1-(y/x)^2) |y| Linear interpolation is used to define the continuous function f(x) corresponding to the samples in f. The first sample f corresponds to f(x=0) and the sampling interval is assumed to be 1. Therefore, the input samples correspond to 0 <= x <= n-1. Samples of f(x) for x > n-1 are assumed to be zero. These conventions imply that g = f + 2*f + 2*f + ... + 2*f[n-1] References: Hansen, E. W., 1985, Fast Hankel transform algorithm: IEEE Trans. on Acoustics, Speech and Signal Processing, v. ASSP-33, n. 3, p. 666-671. (Beware of several errors in the equations in this paper!) Authors: Dave Hale and Lydia Deng, Colorado School of Mines, 06/01/90
Here we see that sudoc shows information about the routines, including their names, usage information (via the function prototype), some theory of how the items are used, published references, and finally the author's names.
As an another example, type:
% sugabor SUGABOR - Outputs a time-frequency representation of seismic data via the Gabor transform-like multifilter analysis technique presented by Dziewonski, Bloch and Landisman, 1969. sugabor <stdin >stdout [optional parameters] Required parameters: if dt is not set in header, then dt is mandatory Optional parameters: dt=(from header) time sampling interval (sec) fmin=0 minimum frequency of filter array (hz) fmax=NYQUIST maximum frequency of filter array (hz) beta=3.0 ln[filter peak amp/filter endpoint amp] band=.05*NYQUIST filter bandwidth (hz) alpha=beta/band^2 filter width parameter verbose=0 =1 supply additional info Notes: This program produces a muiltifilter (as opposed to moving window) representation of the instantaneous amplitude of seismic data in the time-frequency domain. (With Gaussian filters, moving window and multi- filter analysis can be shown to be equivalent.) An input trace is passed through a collection of Gaussian filters to produce a collection of traces, each representing a discrete frequency range in the input data. For each of these narrow bandwidth traces, a quadrature trace is computed via the Hilbert transform. Treating the narrow bandwidth trace and its quadrature trace as the real and imaginary parts of a "complex" trace permits the "instantaneous" amplitude of each narrow bandwidth trace to be compute. The output is thus a representation of instantaneous amplitude as a function of time and frequency. Some experimentation with the "band" parameter may necessary to produce the desired time-frequency resolution. A good rule of thumb is to run sugabor with the default value for band and view the image. If band is too big, then the t-f plot will consist of stripes parallel to the frequency axis. Conversely, if band is too small, then the stripes will be parallel to the time axis. Examples: suvibro | sugabor | suximage suvibro | sugabor | suxmovie n1= n2= n3= (because suxmovie scales it's amplitudes off of the first panel, may have to experiment with the wclip and bclip parameters suvibro | sugabor | supsimage | ... ( your local PostScript utility)
If you compare this output to the output from typing:
% sudoc sugabor
You will see the same output as above, preceeded by a line showing the location of the source code, and followed by the additional paragraphs:
Credits: CWP: John Stockwell, Oct 1994 Algorithm: This programs takes an input seismic trace and passes it through a collection of truncated Gaussian filters in the frequency domain. The bandwidth of each filter is given by the parameter "band". The decay of these filters is given by "alpha", and the number of filters is given by nfilt = (fmax - fmin)/band. The result, upon inverse Fourier transforming, is that nfilt traces are created, with each trace representing a different frequency band in the original data. For each of the resulting bandlimited traces, a quadrature (i.e. pi/2 phase shifted) trace is computed via the Hilbert transform. The bandlimited trace constitutes a "complex trace", with the bandlimited trace being the "real part" and the quadrature trace being the "imaginary part". The instantaneous amplitude of each bandlimited trace is then computed by computing the modulus of each complex trace. (See Taner, Koehler, and Sheriff, 1979, for a discussion of complex trace analysis. The final output for a given input trace is a map of instantaneous amplitude as a function of time and frequency. This is not a wavelet transform, but rather a redundant frame representation. References: Dziewonski, Bloch, and Landisman, 1969, A technique for the analysis of transient seismic signals, Bull. Seism. Soc. Am., 1969, vol. 59, no.1, pp.427-444. Taner, M., T., Koehler, F., and Sheriff, R., E., 1979, Complex seismic trace analysis, Geophysics, vol. 44, pp.1041-1063. Chui, C., K.,1992, Introduction to Wavelets, Academic Press, New York. Trace header fields accessed: ns, dt, trid, ntr Trace header fields modified: tracl, tracr, d1, f2, d2, trid, ntr
There is more information in the sudoc listing, than in the selfdoc listing. The selfdoc is intended as a quick reference, whereas the sudoc listing can provide additional information that we do not necessarily want to see everytime we are, say, simply wanting to know what a particular parameter means, for example.