MATLAB: How to make sure all the elements in an array are less than certain value

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I have an array of type double (name= speed) and it has 72000 values, and i want to write a condition that if any of the elements in speed are less than '800' then do certain calculations, if it is greater than '800' then do certain caluclations

Best Answer

Let's say you want to multiply by 2 if less than 800, and divide by 4 otherwise. Create a mask, then do the assignment of the new values.
mask = speed < 800;
speed(mask) = speed(mask) * 2;
% ~mask (tilde mask) inverts mask and selects speed >= 800
speed(~mask) = speed(~mask) / 4; % fixed typo
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