matrix manipulation
in [Matlab]
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From: Wendy on 6 Apr 2010 09:25 Hi all, I have a matrix a =[ 3 0 3 2 1 3 0 1 9 3 4 0 0 8 1 0]; I want to change all the zeros to NaN. I used [r,c,v]=find(a==0); to find row indices and column indices of all the zero elements. I know I can loop all the elements in the r and c vectors to do that. Is there any way that I can change all the 0 elements to NaN at once. I tried a(r,c) = NaN, but it does not work. Thank you, Wendy
From: Steven Lord on 6 Apr 2010 09:27 "Wendy " <wlq121(a)gmail.com> wrote in message news:hpfcni$b5$1(a)fred.mathworks.com... > Hi all, > > I have a matrix > > a =[ > 3 0 3 2 > 1 3 0 1 > 9 3 4 0 > 0 8 1 0]; > I want to change all the zeros to NaN. I used [r,c,v]=find(a==0); to find > row indices and column indices of all the zero elements. I know I can loop > all the elements in the r and c vectors to do that. Is there any way that > I can change all the 0 elements to NaN at once. I tried a(r,c) = NaN, but > it does not work. Use logical indexing rather than FIND. a(a==0) = NaN; If later on you want to replace the NaN values with something else, using the following will NOT work, because NaN is not equal to anything, not even another NaN: a(a==NaN) = -99; Instead you'd need to use: a(isnan(a)) = -99; -- Steve Lord slord(a)mathworks.com comp.soft-sys.matlab (CSSM) FAQ: http://matlabwiki.mathworks.com/MATLAB_FAQ
From: us on 6 Apr 2010 09:38 "Steven Lord" > Instead you'd need to use: > > a(isnan(a)) = -99; > > -- > Steve Lord or a(a~=a)=-99; % which used to be a bit faster in older ML versions... us
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