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Does Matlab have a command to make data smoother like the smooth command in IDL?

Asked by Nopparat on 9 Sep 2012
Does Matlab have a command to make data smoother like the smooth command in IDL?
For IDL command,
"The SMOOTH function returns a copy of Array smoothed with a boxcar average of the specified width. The result has the same type and dimensions as Array" ( http://idlastro.gsfc.nasa.gov/idl_html_help/SMOOTH.html). The example of the result is following;
The original data
7.79008 4.15141 7.48622
1.69548 6.31630 6.84862
7.00782 2.78159 7.85362
5.91996 0.659594 5.77286
8.38353 3.33698 9.03057
7.64424 0.474168 5.77164
3.62966 8.94523 4.11056
9.33464 1.19968 4.66864
5.79112 3.83709 1.43494
The result data ( IDL> print, smooth(x,3,/edge) )
5.31274 5.66250 6.01227
5.21623 5.58725 5.95827
5.11973 5.51200 5.90428
5.42783 5.47206 5.51628
5.41093 5.25468 5.09842
5.39403 5.03729 4.68056
5.54293 5.28162 5.02030
5.60563 4.92210 4.23857
5.66832 4.56258 3.45685
Thank you in advance.

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3 Answers

Answer by Image Analyst
on 9 Sep 2012
 Accepted Answer

Ordinarily I'd do this:
smoothed_m = conv2(m, ones(3)/9, 'same')
but modified to fix any edge effects:
numerator = conv2(m, ones(3), 'same')
denom = conv2(ones(size(m)), ones(3), 'same')
smoothed_m2 = numerator ./ denom
but it doesn't give you the same output values. However I'm not sure how you got those values. For example, let's take the middle value, which is totally not affected by edge effects. You say it's 5.25468 however in MATLAB:
m9 = [...
5.91996 0.659594 5.77286
8.38353 3.33698 9.03057
7.64424 0.474168 5.77164]
averageValue = mean2(m9)
averageValue =
5.2215
which doesn't match your number. You'll have to define boxcar.

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Answer by Rick Rosson
on 9 Sep 2012

>> doc ones
>> doc filter

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Answer by Sean de Wolski
on 11 Sep 2012

If you have the Curve Fitting Toolbox:

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