On Tue, Apr 29, 2008 at 12:50 PM, Keith Goodman <[EMAIL PROTECTED]> wrote: > On Tue, Apr 29, 2008 at 11:46 AM, Keith Goodman <[EMAIL PROTECTED]> wrote: > > On Tue, Apr 29, 2008 at 11:21 AM, Alan G Isaac <[EMAIL PROTECTED]> wrote: > > > On Tue, 29 Apr 2008, Keith Goodman apparently wrote: > > > > I often use x[i,:] and x[:,i] where x is a matrix and i is > > > > a scalar. I hope this continues to return a matrix. > > > > > > 1. Could you give an example of the circumstances of this > > > use? > > > > In my use i is most commonly an array (i = M.where(y.A)[0] where y is > > a nx1 matrix), sometimes a list, and in ipython when debugging or > > first writing the code, a scalar. It would seem odd to me if x[i,:] > > returned different types of objects based on the type of i: > > > > array index > > idx = M.where(y.A)[0] where y is a nx1 matrix > > x[dx,:] --> matrix > > > > list index > > idx = [0] > > x[idx,:] --> matrix? > > > > scalar index > > idx = 0 > > x[idx,:] --> not matrix > > Here's another use case: > > for i in xrange(x.shape[1]): > xi = x[:,i] > idx = M.where(M.isfinite(xi).A)[0] > xi = xi[idx,:] > # more code > > Also the functions I have written work on matrices. If x[i,:] did not > return a matrix, let's say it returned some other vector type object > that you index with a scalar, then my functions will have to test > whether the input is a full matrix or a vector since the indexing is > different.
And here's a use case that currently doesn't work but would be nice (for me) if it did: x[idx,i] = M.rand(2,1) where x is a matrix, say 4x3, idx is an array with 2 elements, and i is a scalar _______________________________________________ Numpy-discussion mailing list Numpy-discussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpy-discussion
