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Advanced plotting

By the time you reach this point you should know everything you need to start exploring SEPlib on your own. Before finishing up our tour we would like to introduce you to some tricks that might help you to demonstrate your results better.

Often it is useful and spectacular to plot a Wiggle plot on top of a raster plot. That is a little tricky, but not too hard.

First make our windowed input data again (if we don't still have it):

Window < Txx.H min1=.4 max1=.8 max2=1. > Txx_Windowed.H

Now run Ta2vplot once to make the ``background'' raster plot:

Byte < Txx_Windowed.H pclip=100 | \
 Ta2vplot par=plotpar min1=.4 max1=.8 max2=1. min2=.05 \
 out=file1.v head=/dev/null
(For this example we won't need the history file with its parameters any more, just the data file containing vplot graphics commands. The out=file1.v tells Ta2vplot to write the output to ``file1.v''; the head=/dev/null throws the output history file away to the UNIX garbage-can device ``/dev/null''.)

Finally we run Wiggle twice, once with thick ``invisible'' traces and once with half as thick standard yellow ones:

Wiggle < Txx_Windowed.H par=plotpar min1=.4 max1=.8 max2=1. min2=.05 \
 poly=no out=file2.v head=/dev/null plotcol=0 plotfat=10
Wiggle < Txx_Windowed.H par=plotpar min1=.4 max1=.8 max2=1. min2=.05 \
 poly=no out=file3.v head=/dev/null plotfat=5

Note how we had to specify all four limits to be sure that the plots produced by the very different plotting programs Ta2vplot and Wiggle would be compatible. (For some other plot programs even this isn't enough; we also have to turn off the ``padding'' between plot and axes.)

Now for the ``advanced graphics'': to combine the three plots, we use a special pen filter called ``vppen'', which reads in and writes out the vplot graphical files used by SEPlib programs.

vppen file1.v file2.v file3.v erase=once vpstyle=no | tube
vppen is not itself a SEPlib program, hence the lower-case initial letter and why we had to use out= above. (There is a SEPlib version called Vppen that we could have used, but history files become less useful at this point.)

Note that we didn't really need to use vppen above; we could have just done

tube file1.v file2.v file3.v erase=once
directly. It is useful to do such manipulations with vppen because it lets us save the composite plot as a single vplot file, in effect ``flattening'' the composite into a single plot. There is no magic involved here; vppen is a vplot pen filter just like tube, and shares almost all the same code. The only difference is that while tube draws plots on screens, vppen writes out ``vplot graphical language''. Suppose you plot something on your screen using tube with complex options and multiple input files, and want to somehow save your graphical masterpiece in such a way that you can reproduce it again later without so much trouble with options and files. Simple: just replace tube with vppen and redirect the output. You have now saved your masterpiece as a single vplot file.

If you are looking at our example plot on your screen right now you might be wondering why we went to the trouble of creating the ``invisible wiggles'' file file2.v. We hope that after you examine the hardcopy version in Figure [*] the reason should become evident!

Figure 8
vppen file1.v file2.v file3.v erase=once vpstyle=no | pspen


Examining Figure [*] you may also notice there are two titles. While various plot programs like Wiggle and Ta2vplot are consistent in their options for things like where to put the title, which way to put axes, etc, for historical reasons they are not consistent in their defaults. So if you want to get plots from different programs to exactly overlay in general you have to specify everything. Since we did not specify whether to put the title above or below the plot, we got the (different) default for each. You shouldn't have trouble getting around such annoyances. (Usually you just turn off the axes and labels for all the parts but one.)

previous up next print clean
Next: Plot matrices Up: ILLUSTRATIVE EXAMPLES Previous: Applying a filter
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