Conditional extraction of elements from the vector x.
The input vector.
The condition. The following values are supported:
0 - select all x[i] where x[i] < s1
1 - select all x[i] where x[i] > s1
2 - select all x[i] where s1 < x[i] < s2
A real number. See c for details.
A real number (only used if c==2). See c for details.
The result is a scalar or a vector with the selected elements from x.