# How can I give different thresholds to an image

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Joydeb Saha on 11 Apr 2022
Commented: Joydeb Saha on 10 May 2022
How can I give different thresholds to an image? If 'cot' is the image matrix I have attached how can i give a threshold of zero, implying all pixels with non-zero values? Then all pixels above 1, and then all those above 5?

Walter Roberson on 11 Apr 2022
first_answer = cot ~= 0;
second_answer = cot > 1;
third_answer = cot > 5;
If you are trying to categorize the pixels by range, then see discretize()
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Joydeb Saha on 10 May 2022
ncFiles = dir('E:\data\2002\*.nc');
N = length(ncFiles) ;
Q = zeros(N,1) ;
for i = 1:N
ncFile = fullfile(ncFiles(i).folder,ncFiles(i).name) ;
data_Wwind=netcdf(ncFile);
th5 = cot > 3;
B = double(th5);
Q(i)=sum(B(:) == 1);
end
I have used this code to find the total number of pixels those are above threshold 3 for all the data files in the folder. How can I find the mean value of cot for all the data files (every month) only for the pixels those are above threshold three(3)?

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