What is the proper way to address this array when using an if-then statement with logical operators?

What is the best way to create arrays for each C1 , C2 , C3 , and C4 based off a logical if statement? The array RATN is a 6X10 array that is used in the calculation of C1-4. I would like to create a 6x10 array for each C1 , C2 , C3 , and C4 based on the index value in which if RATN is greater than 0.1 but less than 2.0 a value is calculated from one equation, but if the value is greater than 2 the value is calculated from a different equation. As I have it set up now C1 is being populated with values calculated from RATN that are greater than 2.0 with the equation that is supposed to be used for values less than 2.0.

Answer 1

[Voss]

[m,n] = size(ratn);

C1 = zeros(m,n);
C2 = zeros(m,n);
C3 = zeros(m,n);
C4 = zeros(m,n);

idx = ratn < 2 & ratn >= 0.1;

C1(idx) = 0.947 + 1.206.*sqrr(idx) - 0.131.*ratn(idx);
C2(idx) = 0.022 - 3.405.*sqrr(idx) + 0.915.*ratn(idx);
C3(idx) = 0.869 + 1.777.*sqrr(idx) - 0.555.*ratn(idx);
C4(idx) = -0.810 + 0.422.*sqrr(idx) - 0.260.*ratn(idx);

C1(~idx) = 1.232 + 0.832.*sqrr(~idx) - 0.008.*ratn(~idx);
C2(~idx) = -3.813 + 0.968.*sqrr(~idx) - 0.260.*ratn(~idx);
C3(~idx) = 7.423 - 4.868.*sqrr(~idx) + 0.869.*ratn(~idx);
C4(~idx) = -3.839 + 3.070.*sqrr(~idx) - 0.600.*ratn(~idx);

[zachary owen]

Thank you! If I wanted to find more documentation on this what topics should I search?

[Voss]

You're welcome! This approach uses "logical indexing".

https://www.mathworks.com/company/newsletters/articles/matrix-indexing-in-matlab.html

https://www.mathworks.com/matlabcentral/answers/129-how-does-logical-indexing-work

Let me know if you have any other questions.