Sum of elements in 2D matrix greater tha 150

I wouls like to find the sum of elements in a 2D matrix (254*318) with elements value greater than 150. but I get the code run but the answer is wrong if nayone could find the erro would be very helpful.R_10M is the name of the matrix

for a = 1:254

for b = 1:318

if (R_10M(a,b) > 150)

value = sum(sum(R_10(a,b)));

end

end

end

[dileesh pv]

The loops in MATLAB is generally slow. MATLAB is pretty good with opearating on matrices. For a faster and efficient execution use the inherent strengths of MATLAB.

This can be done in a single step;

s = sum( R_10M (R_10M >150));

A detailed example code is given below;

R_10M = round(rand(254,318)*300); % Matrix with random entry

s = sum (R_10M (R_10M >150)); % Required sum

% Above line of code can be deconstructed into two steps as given below

a1= (R_10M >150); % Generate the logical array where the non-zero entries 
% are at the indices of elements whose values are higher than 150

s1=sum(R_10M(a1)); % sum up the elements corresponding to the non-zero 
% entries in the logical array a1

This is exactly what John D'Errico has suggested. I just added little detailed explanation to it.

[John D'Errico]

@dileesh pv

Thank you for the explanations. I should have done that in my answer.

Answer 1

[VBBV]

for a = 1:254
    for b = 1:318
        if (R_10M(a,b) > 150)
            value(a,b) = R_10M(a,b); % use row and column indices for values matrix required before summing, 
        end
    end
end
V = sum(sum(value)); % singular value 
VV = sum(value); % vector of summed values

What you intend to sum of values > 150 in your matrix R_10, needs further specific conditions e.g. summing row wise or column wise ? or both (like you are doing inside if condition) ?

[Sasidharan Subramani]

Sorry there was an error in the code the name of the matrix is R_10M in both the line. I want to find all the elements in the matrix with values greater than 150 not specifically row wise or coloum wise.I want the answer to be as a single number ot in the form of a matrix.

[VBBV]

Ok. Did you get any error after changing to R_10M ?

[Sasidharan Subramani]

yes, got it thank you.

Answer 2

[John D'Errico]

Time to learn to use MATLAB as it is designed to be used.

value = sum(R_10M(R_10M > 150));

One line. No loops are necessary.