From: David Winsemius <dwinsemius_at_comcast.net>

Date: Sun, 27 Mar 2011 18:30:48 -0400

*>>
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> http://www.google.com/search?sclient=psy&hl=en&q=R+cran+median+filter

Date: Sun, 27 Mar 2011 18:30:48 -0400

On Mar 27, 2011, at 1:07 PM, Mike Marchywka wrote:

> You obviously want to delegate inner loops to R packages that > execute as native, hopefully optimized, code. > Generally a google search that starts with "R CRAN" will help. > In this case it looks like a few packages available,

> http://www.google.com/search?sclient=psy&hl=en&q=R+cran+median+filter

Did you find any that include a 2D median filter? All the ones I looked at were for univariate data.

-- David.Received on Sun 27 Mar 2011 - 22:42:50 GMT

>>

>> ----------------------------------------

>>> Date: Sun, 27 Mar 2011 07:56:11 -0700>>> From: chuan_zl_at_hotmail.com>>> To: r-help_at_r-project.org>>> Subject: [R] Asking Favor For the Script of Median Filter>>>>>> Hello,everybody. My name is Chuan Zun Liang. I come from Malaysia.>>> I am just>>> a beginner for R. Kindly to ask favor about median filter. The>>> problem I>>> facing as below:>>>>>>>>>> x<-matrix(sample(1:30,25),5,5)>>>> x>>> [,1] [,2] [,3] [,4] [,5]>>> [1,] 7 8 30 29 13>>> [2,] 4 6 12 5 9>>> [3,] 25 3 22 14 24>>> [4,] 2 15 26 23 19>>> [5,] 28 18 10 11 20>>>>>> This is example original matrices of an image. I want apply with>>> median>>> filter with window size 3X# to remove salt and pepper noise in my>>> matric.>>> Here are the script I attend to writing.The script and output>>> shown as>>> below:>>>>>>> MedFilter<-function(mat,sz)>>> + {out<-matrix(0,nrow(mat),ncol(mat))>>> + for(p in 1:(nrow(mat)-(sz-1)))>>> + {for(q in 1:(ncol(mat)-(sz-1)))>>> + {outrow<-median(as.vector(mat[p:(p+(sz-1)),q:(q+(sz-1))]))>>> + out[(p+p+(sz-1))/2,(q+q+(sz-1))/2]<-outrow}}>>> + out}>>>>>>> MedFilter(x,3)>>> [,1] [,2] [,3] [,4] [,5]>>> [1,] 0 0 0 0 0>>> [2,] 0 8 12 14 0>>> [3,] 0 12 14 19 0>>> [4,] 0 18 15 20 0>>> [5,] 0 0 0 0 0>>>>>> Example to getting value 8 and 12 as below:>>>>>> 7 8 30 8 30 29>>> 4 6 12 (median=8) 6 12 5 (median=12)>>> 25 3 22 3 22 14>>>>>> Even the script can give output. However, it is too slow. My image>>> size is>>> 364*364. It is time consumption. Is it get other ways to improving>>> it?>>>>>> Best Wishes>>> Chuan

-- David Winsemius, MD West Hartford, CT ______________________________________________ R-help_at_r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.

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