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Mode function for floating point arrays [message #85114]

Fri, 05 July 2013 11:55

Matthew Argall
Messages: 286
Registered: October 2011

Senior Member

PEAMBLE:
I need a function that finds the mode of a floating point array. I have read David Fanning's article about integer arrays

http://www.idlcoyote.com/code_tips/mode.html

From this article about majority voting, it seems like "Hist_ND" works for floating point values, but I have no experience with the magic of HISTOGRAM

https://groups.google.com/forum/#!searchin/comp.lang.idl-pvw ave/Mode$20of$20a$20floating$20point$20array/comp.lang.idl-p vwave/YZK2ey-O5sE/9fLvx_AG2IAJ

QUESTION:
Here is my attempt. Can anyone make it better/faster?

;-----------------------------------------------------
function mrmode, array, $
EPSILON=epsilon
compile_opt idl2

;Number of points in ARRAY
npts = n_elements(array)

;Default value for EPSILON
if n_elements(epsilon) eq 0 then epsilon = 1d-5

;[index, count] for keeping track of mode statistics
mode_count = lonarr(2, npts)

;Store first ~unique number. Count the how many ~unique numbers there are.
mode_count[*,0] = [0,1]
nunique = 1

;Step through all points in ARRAY
for i = 1, npts - 1 do begin
match_found = 0

;Try to pair the new point with other mode candidates
for j = 0, nunique - 1 do begin
if array[i] gt array[mode_count[0,j]]-epsilon && $
array[i] lt array[mode_count[0,j]]+epsilon $
then begin

mode_count[1,j] += 1
match_found = 1
endif
endfor

;If no match was found, create a new mode candidate
if match_found eq 0 then begin
mode_count[*,nunique] = [i,1]
nunique += 1
endif
endfor

;Get the mode
void = max(mode_count[1,*], iMode)
mode = array[mode_count[0,iMode]]

return, mode
end

;----------------------------------------------------------- ----------
;Example Program (IDL> .r mrmode) /////////////////////////////////////////
;----------------------------------------------------------- ----------
array = [1.2, 0.1, 3.3, 0.1, 2.0, 3.3, 4.8, 1.2, 0.1, 0.1, 6.7, 3.3]
mode = MrMode(array)
print, FORMAT='(%"The mode is: %f")', mode

end

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[Message index]

		Mode function for floating point arrays By: Matthew Argall on Fri, 05 July 2013 11:55
		Re: Mode function for floating point arrays By: Rob Klooster on Mon, 08 July 2013 01:01
		Re: Mode function for floating point arrays By: Rob Klooster on Mon, 08 July 2013 01:24
		Re: Mode function for floating point arrays By: Matthew Argall on Tue, 09 July 2013 06:36
		Re: Mode function for floating point arrays By: David Fanning on Tue, 09 July 2013 07:01
		Re: Mode function for floating point arrays By: Rob Klooster on Wed, 17 July 2013 07:08
		Re: Mode function for floating point arrays By: Matthew Argall on Fri, 19 July 2013 16:50
		Re: Mode function for floating point arrays By: Rob Klooster on Mon, 22 July 2013 04:24

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