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4. where


Get indices where an integer array is non-zero


Array_Type where (Array_Type a)


The where function examines an integer array a and returns a 2-d integer array whose rows are the indices of a where the corresponding element of a is non-zero.


Consider the following:

    variable X = [0.0:10.0:0.01];
    variable A = sin (X);
    variable I = where (A < 0.0);
    A[I] = cos (X) [I];
Here the variable X has been assigned an array of doubles whose elements range from 0.0 through 10.0 in increments of 0.01. The second statement assigns A to an array whose elements are the sin of the elements of X. The third statement uses the where function to get the indices of the elements of A that are less than 0.0. Finally, the last statement substitutes into A the cos of the elements of X at the positions of A where the corresponding sin is less than 0. The end result is that the elements of A are a mixture of sines and cosines.
See Also

array_info, sin, cos

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