Tuesday, August 9. 2011
Program of the month: sfgraph
sfgraph belongs to the family of plotting programs and is used for plotting explicitly defined 2-D curves.
Here are 10 basic facts about this program:
Here are 10 basic facts about this program:
- sfgraph shares most of its parameters with some other 2-D plotting programs (sfgrey, sfcontour, sfwiggle). These common parameters can be accessed by running sfdoc stdplot.
The following plot from rsf/rsf/sfgraph is using parameters grid=y gridcol=5 pad=n and some creative changes of fonts in the title.
- If the input to sfgraph is real, it is understood as representing a regularly sampled 1-D function Y(X), where X is sampled according to n1=, o1=, and d1= parameters in the input file.
- If the input is complex, its real part is taken as X, and the imaginary part is taken as Y. If the input is real initially, it is easy to turn it into complex by using sfcmplx or sfdd.
- If the n2 parameter in the input is greater than 1, multiple curves are plotted.
The following plot from rsf/rsf/sfmath shows plots of closed curves defined by a complex-valued input.
- If the n3 or any of the larger dimensions is greater than 1, the plot becomes a movie.
- By default, the graphs are plotted with lines. One can control the line appearance with generic parameters dash=, plotcol=, plotfat=.
- If symbol= is specified, the graph is plotted with the given symbols. The size of the symbol is controlled with symbolsz=.
The following plot from sep/precon/oned is created with symbol="md" symbolsz=7.
- The displayed function can be changed from Y(X) to X(Y) by using transp= parameter.
The following plot from jsg/nmo3/azimuthtest is created with transp=y yreverse=y symbol=+ symbolsz=4.
- The ranges of X and Y are selected automatically but can be controlled with min1=, max1=, min2=, max2=. If you want automatic ranges, but no padding around minimum and maximum values, use pad=n.
- sfgraph avoids plotting infinite or NaN (not a number) values.
The following plot from jsg/seislet/sin2 contained dashed lines created with dash=1,2,0.
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sfsmooth, one of the most useful Madagascar programs, implements smoothing by triangle filtering. The idea of triangle filtering is explained in Jon Claerbout's books Processing versus Inversion and Image Estimation by Example. You can find the explan
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Tracked: May 06, 08:10
sfderiv applies the first derivative filter. The algorithm implemented in this program is described in the paper Pei, S.-C., and P.-H. Wang, 2001, Closed-form design of maximally flat FIR Hilbert transformers, differentiators, and fractional delaye
Tracked: May 06, 08:11
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Tracked: Jun 02, 06:46
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Tracked: Jun 04, 05:46
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sfpick performs automatic picking from semblance-like panels. The underlying algorithm is described in Appendix B of the paper Velocity analysis using AB semblance and is inspired by the method of virtual endoscopy in medical imaging. The following
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Tracked: Sep 09, 12:52
sfpick performs automatic picking from semblance-like panels. The underlying algorithm is described in Appendix B of the paper Velocity analysis using AB semblance and is inspired by the method of virtual endoscopy in medical imaging. The following
Tracked: Sep 09, 12:52
sfkirmod is a program for modeling seismic reflection data using the Kirchhoff method. According to this method, the reflection response is computed by integrating over the reflector surface. For a theoretical derivation, see, for example, Haddon, R. A
Tracked: Oct 13, 19:46
sfbandpass implements bandpass filtering using the Butterworth algorithm. The desired bandwidth is specified by low and high frequencies (in Hertz) flo= and fhi=. A continuous low-pass Butterworth filter is given by The actual filtering is imp
Tracked: Nov 18, 13:45