| Histogram looks like spiky bars [message #53063] |
Fri, 16 March 2007 08:14  |
rpertaub@gmail.com
Messages: 43
Registered: January 2007
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Member |
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Hi,
I have an image for which I want to make a histogram. I just do plot,
histogram(image) with xrange being my 14 bit image size (~16000).
ANyway, what I get is a bunch of vertical lines of different lengths.
I want a smooth curve, not discrete lines.
How do i do that?
thanks!!
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| Re: Histogram looks like spiky bars [message #53110 is a reply to message #53063] |
Tue, 20 March 2007 12:27  |
MarioIncandenza
Messages: 231
Registered: February 2005
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Senior Member |
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On Mar 16, 8:14 am, "rpert...@gmail.com" <rpert...@gmail.com> wrote:
> Hi,
> I have an image for which I want to make a histogram. I just do plot,
> histogram(image) with xrange being my 14 bit image size (~16000).
> ANyway, what I get is a bunch of vertical lines of different lengths.
> I want a smooth curve, not discrete lines.
> How do i do that?
> thanks!!
There are two routines out there called HIST_PLOT. One is from Liam
Gumley and can be found at http://www.cis.rit.edu/~dwmpci/HTML_DOC/plotting_help.html
(also see his extensive bag o' tricks at http://cimss.ssec.wisc.edu/~gumley/).
The other is from Gelu Nita and can be found here:
http://achilles.nascom.nasa.gov/~zarro/php/ssw_print.php?fil e=$SSW/radio/ovsa/idl/util/hist_plot.pro.
I use the Gumley routine, though over the years I have modified it
almost into unrecognizability. But if you're just getting into this
problem, try them both see which you like better, both are very simple
routines.
Good luck!
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| Re: Histogram looks like spiky bars [message #53122 is a reply to message #53063] |
Mon, 19 March 2007 22:35 |
Sven Geier
Messages: 17
Registered: July 2002
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Junior Member |
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rpertaub@gmail.com wrote:
> Hi,
> I have an image for which I want to make a histogram. I just do plot,
> histogram(image) with xrange being my 14 bit image size (~16000).
> ANyway, what I get is a bunch of vertical lines of different lengths.
> I want a smooth curve, not discrete lines.
> How do i do that?
> thanks!!
At the risk of asking something stupid:
Are you sure that all the possible values actually occur in your image? I'm
asking because I once had a funky image that I didn't understand the
histogram of at all - until I realized that in the processing there was a
step where floats got truncated to integers and in that step I was losing
all non-integer values and in the end the values I was histogramming over
were integer multiples of some certain scaling factor (and the histogram
plotted thin spikes for those values and zeros for any other number).
Just an idea...
- S
--
http://www.sgeier.net
My real email address does not contain any "Z"s.
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