| Re: Box-Whisker plots in IDL [message #55395 is a reply to message #55393] |
Mon, 20 August 2007 13:56   |
David Fanning
Messages: 11724
Registered: August 2001
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Senior Member |
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teich@atmsci.msrc.sunysb.edu writes:
> Hi, Suppose data is something simple like:
>
> data=[2,3,5,7,7,10,11,11,12,15,16,17,17]
>
> I get a 75th quartile of 11.0. Shouldn't I get around 15?
JD will have to explain the difference between BINSIZE
and NBINS to us again. (And I think he is in China for
a couple of weeks.) But I got strange results with my
HISTOGRAM method, too. Here is a slightly revised program:
data=[2,3,5,7,7,10,11,11,12,15,16,17,17]
;box plot needs min, max, median which are straight forward:
minVal = min(data)
maxVal = max(data)
medianVal = median(data,/even)
; Find the quartiles.
h = Histogram(data, NBINS=4, REVERSE_INDICES=ri, $
MIN=minVal, MAX=maxVal)
qtr_25th = Median(data[ri[ri[0]:ri[2]-1]])
qtr_75th = Median(data[ri[ri[2]:ri[4]-1]])
Print, minVal, maxVal, medianVal, qtr_25th, qtr_75th
END
And the result I get with the new data:
2 17 11.0000 7.00000 16.0000
--
David Fanning, Ph.D.
Fanning Software Consulting, Inc.
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Sepore ma de ni thui. ("Perhaps thou speakest truth.")
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