How do I write a MATLAB code for A (in body) that doubles the elements that are greater than 6, and raises to the power of 2 the elements that are negative but greater than -2?

A=[5 10 -3 8 0; -1 12 15 20 -6]

Answer 1

[sixwwwwww]

Here is code for your problem

A=[5 10 -3 8 0; -1 12 15 20 -6];
dim = size(A);
B = nan(dim(1), dim(2));
for i = 1:dim(1)
    for j = 1:dim(2)
        if A(i,j) >= 6
            B(i,j) = 2 * A(i,j);
        else if (A(i,j) < 6 && A(i,j) > -2)
                B(i,j) = A(i,j) ^ 2;
            end
        end
    end
end

Good luck

[Sam]

Thanks! How do I maintain the value of the numbers in the matrix that are not changed through the calculations (*2 or ^2)?

[sixwwwwww]

A=[5 10 -3 8 0; -1 12 15 20 -6];
dim = size(A);
B = nan(dim(1), dim(2));
for i = 1:dim(1)
    for j = 1:dim(2)
        if A(i,j) >= 6
            B(i,j) = 2 * A(i,j);
        else if (A(i,j) < 6 && A(i,j) > -2)
                B(i,j) = A(i,j) ^ 2;
            else
                B(i,j) = A(i,j);
            end
        end
    end
end

Here is the code which maintain values which are not used in *2 or ^2 operations. Good luck

[Sam]

Thanks for clarifying!

[Image Analyst]

But it's still doesn't do what you asked. Specifically

A(i,j) < 6 && A(i,j) > -2

does not select "elements that are negative but greater than -2" as you asked for. Use Kelly's answer instead which does it correctly. Plus that solution uses a vectorized approach which is faster and the more MATLAB-ish way to do it.

Answer 2

[Kelly Kearney]

The loops are unnecessary:

A = [5 10 -3 8 0; -1 12 15 20 -6];
A(A > 6) = A(A > 6) .* 2;
A(A < 0 & A > -2) = A(A < 0 & A > -2).^2

A =

     5    20    -3    16     0
     1    24    30    40    -6

[Sam]

Thanks. I like the solution w/o the loops!