comp.lang.idl-pvwave archive: archive » IDL Average Value Graphs

Home » Public Forums » archive » IDL Average Value Graphs

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: IDL Average Value Graphs [message #61456 is a reply to message #61413]

Wed, 16 July 2008 11:18

Jeremy Bailin
Messages: 618
Registered: April 2008

Senior Member

On Jul 15, 4:51 pm, andyb...@gmail.com wrote:
> Hello, I was wondering if IDL has any built-in methods for two similar
> things.
> 1. Basically cut the image like a pizza (for a variable number of
> slices) and average the values in each slice to create a plot of
> average pixel value as a function of angle
> 2. Do the same thing, but plot the average pixel value as a function
> of radius, (concentric circles).
>
> I was going to write my own method, but it would be complicated
> converting angled lines or circles into pixels.
>
> Thanks a lot, Andy

I don't know of anything built-in, but I've written similar sorts of
things quite a lot using HISTOGRAM, and it's pretty straight-
forward... here's a (UNTESTED!) hack at it, assuming that your image
is called "image", is centered at pixel x0,y0, and you want n_azimuth
pie slices and radial bins of width dr:

indeximage=array_indices(image, lindgen(n_elements(image)))
pixelradii = sqrt( (indeximage[0,*]-x0)^2 + (indeximage[1,*]-y0)^2 )
pixelazimuth = atan(indeximage[1,*], indeximage[0,*])

radhist = histogram(pixelradii, min=0, bin=dr, reverse_indices=radri)
nrad=n_elements(radhist)
azhist = histogram(pixelazimuth, min=0, bin=2.*!pi/n_azimuth,
reverse_indices=azri)
naz=n_elements(azhist)

radial_mean = fltarr(nrad)
azimuthal_mean = fltarr(naz)
for i=0l,nrad-1 do if radhist[i] gt 0 then radial_mean[i] =
mean(image[radri[radri[i]:radri[i+1]-1]])
for i=0l,naz=1 do if azhist[i] gt 0 then azimuthal_mean[i] =
mean(image[azri[azri[i]:azri[i+1]-1]])

-Jeremy.

-Jeremy.

Report message to a moderator

[Message index]

		IDL Average Value Graphs By: andybohn on Tue, 15 July 2008 13:51
		Re: IDL Average Value Graphs By: David Fanning on Thu, 17 July 2008 08:33
		Re: IDL Average Value Graphs By: andybohn on Thu, 17 July 2008 10:55
		Re: IDL Average Value Graphs By: Jeremy Bailin on Wed, 16 July 2008 11:18
		Re: IDL Average Value Graphs By: andybohn on Thu, 17 July 2008 18:11
		Re: IDL Average Value Graphs By: David Fanning on Thu, 17 July 2008 16:02
		Re: IDL Average Value Graphs By: Jean H. on Fri, 18 July 2008 10:20
		Re: IDL Average Value Graphs By: Jean H. on Thu, 17 July 2008 14:52
		Re: IDL Average Value Graphs By: David Fanning on Thu, 17 July 2008 12:09
		Re: IDL Average Value Graphs By: andybohn on Thu, 17 July 2008 11:02

Previous Topic:	Something Has Changed
Next Topic:	QHULL/VORONOI question

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Sat Oct 11 02:51:46 PDT 2025

Total time taken to generate the page: 0.79848 seconds