Hello,
I wanted to do the following thing that I do in Matlab (on a bigger problem), setting the values of a part of a matrix with indexing:
a=floor(rand(5,5)*10) % make an example matrix to work on
a =
2 4 7 9 8 6 9 2 5 2 6 3 5 1 8 1 5 6 1 2 1 2 8 2 9
ind=[2,4]
ind =
2 4
a(ind,ind)=a(ind,ind)+100
a =
2 4 7 9 8 6 109 2 105 2 6 3 5 1 8 1 105 6 101 2 1 2 8 2 9
===========================
In numpy, the same gives:
In [11]:a=floor(random.rand(5,5)*10) In [14]:a Out[14]: array([[ 7., 7., 8., 1., 9.], [ 0., 4., 9., 0., 5.], [ 4., 3., 7., 8., 3.], [ 2., 0., 4., 2., 4.], [ 9., 5., 0., 9., 9.]])
In [15]:ind=[1,3]
In [20]:a[ind,ind]+=100
In [21]:a Out[21]: array([[ 7., 7., 8., 1., 9.], [ 0., 104., 9., 0., 5.], [ 4., 3., 7., 8., 3.], [ 2., 0., 4., 102., 4.], [ 9., 5., 0., 9., 9.]])
which only replaces 2 values, not all the values in the row,col combinations of [1,1],[1,2],etc...[3,3] like matlab. Is there a preferred way to do this, which I think should be fairly common. If I know that the indices are regular (like a slice) is there a way to do this?
thanks,
Brian Blais