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Re: histogram and binsize problems [message #34247 is a reply to message #34246]

Thu, 27 February 2003 11:26

Chad Bender
Messages: 21
Registered: July 2001

Junior Member

> You may wish to check out the HIST_PLOT procedure I wrote as an example
> program for my book (Chapter 6, pp 260-262):

Thanks for the suggestions. Liam, your routine gives me the same result
as I was getting with just:
plot, findgen(31), histogram(data,min=0.0,max=0.15,binsize=0.005), psym=10

I looked through it briefly, and it is doing enough strange things to
convience me that how histogram sets up its bins is not trivial. However,
using it does not get rid of the bins with value 0.

I tried a few other things to see if I could figure out something of what
histogram is doing. It's obvious from something like the following that
histogram has rounding issues at the bin boundaries.
IDL> test=findgen(31)*0.005
IDL> plot, test, histogram(test, min=0.0, max=0.15, binsize=0.005),
psym=10
IDL> plot, test, histogram(test, binsize=0.005), psym=10

But from expanding the min and max by +-binsize/2, I get almost the
expected result
IDL> hist=histogram(test, min=-0.0025, max=0.1525, binsize=0.005)
IDL> help, hist
HIST LONG = Array[32]
IDL> plot, findgen(32)*0.005, hist, psym=10, ystyle=3, xstyle=3

From this I can see that the last bin is empty. It
falls outside the range I specified by min and max (ie. it covers
0.1525-0.1575). So why does IDL create it at all?

Chad

--
#############################
Chad Bender
Dept of Physics and Astronomy
SUNY Stony Brook
cbender@mail.astro.sunysb.edu

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[Message index]

		Re: histogram and binsize problems By: JD Smith on Thu, 27 February 2003 13:12
		Re: histogram and binsize problems By: David Fanning on Thu, 27 February 2003 12:00
		Re: histogram and binsize problems By: K. Bowman on Thu, 27 February 2003 11:31
		Re: histogram and binsize problems By: Chad Bender on Thu, 27 February 2003 11:26
		Re: histogram and binsize problems By: Liam E. Gumley on Thu, 27 February 2003 10:36
		Re: histogram and binsize problems By: David Fanning on Thu, 27 February 2003 09:11

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