Scan for elements of matrix, to limit them in an interval, and change them.

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Isai Fernandez
Isai Fernandez 2018-4-15
评论： Stephen23 2018-4-15
I am learning to write my programs in Matlab.
I want to limit the value of the matrix elements for some interval, and if they don't accomplish the condition, change them.
For example, for a matrix:
A = |a_11 a_12|
|a_21 a_22|
Limit the values of a_ii for an interval:
-m >= a_ii <= +m.
In my code, the values of the matrix come from other calculation, but I want to limit the values of them; in any case, if a_ii is greater of +m, so change this element of the matrix for +m, the same for -m, but if they are within the limits, let them with its value.
I don't know the size of the matrix, because it depends on preview calculation. Indeed, my matrix always will be a column matrix.
P.D. Sorry for my poor english.

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Walter Roberson
Walter Roberson 2018-4-15
a_ii = min( +m, max( -m, a_ii) );
max(-m, a_ii) takes the maximum of -m and a_ii, which is going to be -m if a_ii < -m, but otherwise would be a_ii . So now we have put a lower bound on a_ii . Then min( +m, that result) is going to be the minimum of +m and the result, which is going to be +m if the result exceeds +m and otherwise would be unchanged. So by the end of the min() we have a value that is constrained to -m to +m
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Walter Roberson
Walter Roberson 2018-4-15
In the above code, a_ii can be a matrix of all of the elements you wish to limit in this way. You can use this code even for the elements that might be already in range -- no need to select only the ones out of range first.
Stephen23
Stephen23 2018-4-15
"Do you mean, one by one?"
No, you don't need any loops or "one-by-one" operations. You can use this method with the entire array at once: simply supply the limit values as scalars (if they are the same for all array elements) or as arrays of the same size.

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