MIME-Version: 1.0
Date: Mon, 6 Feb 1995 16:25:17 -0700
To: igor@pica.army.mil
From: "Michael Blanpied, USGS" <mblanpied@isdmnl.wr.usgs.gov>
Subject: Decimation procedure attached

Fellow datacrunchers,

Several people have emailed in response to my offer to post a routine for
doing "intelligent" decimation on parametric data, so I am enclosing it as
attachment to this message. (My apologies to the many of you who have no
need for it or who have written superior versions yourselves.) The routine
is useful for eliminating needless redundancy in your data while retaining
all the interesting parts.

The file contains a macro called PassDataThroughBox() and a function called
QuikChop(). Further comments in the header. Contrary to my earlier
statement, the function lacks the ability to average over the "skipped"
points, though this feature could be easily added.

To see how it works, open a new experiment, load and compile the procedure
file, then issue the following set of commands:

|Create a noisy sine wave:
make/n=100 wave0=p
make/n=100 wave1=sin(p/15)+gnoise(0.1)
|Write points when X changes by 5 or Y changes by 0.25:
PassDataThroughBox("wave0","wave1","wave0_b","wave1_b",5,0.25,2,1)
|Display results:
display wave1 vs wave0; append wave1_b vs wave0_b
ModifyGraph
mode=4,marker(wave1)=7,opaque(wave1)=1,rgb(wave1)=(3,52428,1);DelayUpdate
ModifyGraph marker(wave1_b)=18,rgb(wave1_b)=(52428,1,1)

|Then issue the following one-by-one and watch the graph change:

|Write points when X changes by 5 or Y changes by 0.1:
PassDataThroughBox("wave0","wave1","wave0_b","wave1_b",5,0.1,2,1)

|Write points when Y changes by 0.35 (ignore X):
PassDataThroughBox("wave0","wave1","wave0_b","wave1_b",1e9,0.35,2,1)

|Write points when X changes by 5 (ignore Y):
PassDataThroughBox("wave0","wave1","wave0_b","wave1_b",5,1e9,2,1)

|Keep all points (Ybox = 0):
PassDataThroughBox("wave0","wave1","wave0_b","wave1_b",5,0,2,1)


I welcome feedback, suggestions for improvements, or improved versions.

Cheers,
Mike Blanpied





Attachment converted: Apps:PassDataThroughBox Proc. (TEXT/IGR0) (00004E04)

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