[Numpy-discussion] simple question

[Keith Goodman]

On 7/5/06, Mathew Yeates <myeates at jpl.nasa.gov> wrote:
> What is the typical way of doing the following
> starting with a 0 matrix, set all values to 1 when a certain condition
> is met, set to -1 when another condition is met, left alone if neither
> condition is met.

This works on recent versions of numpy:

>> x = asmatrix(zeros((2,2)))

>> x

matrix([[0, 0],
       [0, 0]])

>> y = asmatrix(rand(2,2))

>> y

matrix([[ 0.85219404,  0.48311427],
       [ 0.41026966,  0.2184193 ]])

>> x[y > 0.5] = 1

>> x[y < 0.5] = -1

>> x

matrix([[ 1, -1],
       [-1, -1]])