SciPy Recipes

Creating a masked array from a condition

The numpy.ma module has a collection of functions geared towards common ways of constructing masked arrays. The following code illustrates how to create an array where all entries between 4 and 6 are masked:

x = np.array([       [i+j for j in range(i, i+5)]        for i in range(5)])xm = ma.masked_inside(x, 4, 6)

In this code, we first generate the following array:

[[ 0  1  2  3  4] [ 2  3  4  5  6] [ 4  5  6  7  8] [ 6  7  8  9 10] [ 8  9 10 11 12]]

We then use the ma.masked_inside(x, 4, 6) function call to mask all elements of the array that are in the interval [4,6], resulting in the following masked array:

[[0 1 2 3 --] [2 3 -- -- --] [-- -- -- 7 8] [-- 7 8 9 10] [8 9 10 11 12]]

Notice that the endpoints are included in the ...