How delete arrays with numpy

Question

I'm trying to delete the arrays of this matrix:

https://mega.co.nz/#!wNo2Cb5T!0EoALVMtTJbC1-7dgFLbVK8deinL8tGK0eI68bRCOwo

I need delete only the arrays that have -1 in the last column, I tried this but doesn't work:

for i in range (m):
     if matriz[i][8]==-1:
     matriz=numpy.delete(matriz,i,0)

Any idea? :)

What do you mean: 'It doesn't work?'. Does it do nothing? Does it crash? Does it produce an adverse result? — anon582847382
– anon582847382, Commented Oct 25, 2014 at 12:49
The problem is that the output still have arrays with "-1" in the last column. — Sadae
– Sadae, Commented Oct 25, 2014 at 12:54

John Zwinck · Accepted Answer · 2014-10-25 12:54:18Z

2

You actually shouldn't "delete" here, you should just use indexing:

good_rows = matriz[:,8] != -1
good_matriz = matrix[good_rows]

This will give you the rows where the 9th column is not -1, and it's more efficient than deleting one column at a time because it doesn't copy your data.

answered Oct 25, 2014 at 12:54

John Zwinck

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