# Comparing value in m x n matrices to find its index

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Tifani Utami on 28 Apr 2016
Commented: Tifani Utami on 3 May 2016
Hi, I have one set of data that I need to compare it with different size of data. So, as it stated in this code below, the threshold will be 3, 3.5, 4, 4.5 ..... I have to compare each threshold with all available data in variable GtrecMRCG2 then get its index. after all data compared, I need to check it with remaining threshold in variable thresholdVAR.
I wrote this based on my understanding. but it doesn't work because the dimension is mismatched. Thank you so much and big appreciation to those who want to give me advises. :)
threshold = 3;
thresholdVAR=[threshold 0 0 0 0 0 0 0 0];
GtrecMRCG2= [ 5 8 9 6 2 5 2 4 6 3 8 9 11];
for ii=1:9
thresholdVAR(ii+1:end)= thresholdVAR(ii)+ 0.5;
end
for idxm=1:length(thresholdVAR)
for idxn = 1:length(GtrecMRCG2)
idxalarmMRCG (1:length(thresholdVAR),1:length(GtrecMRCG2))= find(GtrecMRCG2(idxm,idxn)>=thresholdVAR(idxm,idxn));
end
end
CS Researcher on 1 May 2016
Not exactly sure what you are trying to achieve but you should see the line with the code:
find( thresholdVAR(idxm:sza(1),idxn:sza(2)) < GtrecMRCG2(1:sza(1),1:sza(2)));
Your thresholdVAR and GtrecMRCG2 are not 2D matrices. They both are 1D vectors.
Also, you don't need a loop to initialize the thresholdVAR. You can just do this:
thresholdVAR = 3:0.5:7;
Tifani Utami on 2 May 2016
example first value of threshold. when threshold is 3, compare it with the value which in GtrecMRCG2 variable. find the index containing value that greater equal than GtrecMRCG2.
is_greater_equal will be [ 1 2 3 4 6 8 9 10 11 12 13]
then move to the next threshold which is 3.5
is_greater_equal = [ 1 2 3 4 6 8 9 10 11 12 13]
the process will keep going until all value which in GtrecMRCG2 compared with last threshold. my question is how to manipulate the output or to construct a new matrices as a result of comparison between two different matrices length.

Ilham Hardy on 2 May 2016
Something like this?
thresholdVAR = 3:0.5:7;
GtrecMRCG2= [ 5 8 9 6 2 5 2 4 6 3 8 9 11];
% preallocate
DesMat = zeros(length(thresholdVAR),length(GtrecMRCG2));
for oneL = 1:length(thresholdVAR)
[r,c,v] = find(GtrecMRCG2>thresholdVAR(oneL));
DesMat(oneL,c) = GtrecMRCG2(c);
end
Tifani Utami on 3 May 2016
thanks a lot. I finally able to use the result to find its average value.