mask

Syntax

mask(X, Y)

Arguments

X is a scalar/vector/matrix.

Y is a conditional expression that generates true or false.

Details

Apply Y on each element of X. If the result is false, keep the element; if the result is true, change it to NULL. The result is of the same length as X.

Examples

$ x=1..10
$ mask(x, x>6);
[1,2,3,4,5,6,,,,]

$ m=matrix(1 2 3, 4 5 6, 7 8 9);
$ m;

#0	#1	#2
1	4	7
2	5	8
3	6	9

$ mask(m, m<6);

#0	#1	#2
		7
		8
	6	9