[Numpy-discussion] untenable matrix behavior in SVN
Keith Goodman
kwgoodman@gmail....
Tue Apr 29 13:46:41 CDT 2008
On Tue, Apr 29, 2008 at 11:21 AM, Alan G Isaac <aisaac@american.edu> 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
> 2. Would any or all of the following be just as good
> a result?
> a. 1d matrix
> b. row and column vectors (1d but "oriented" for
> linear algebra purposes)
For me, having arrays and matrices is confusing enough. Adding row and
column objects sounds even more confusing.
> 3. If 2a. and 2b. are no good for you,
> a. would e.g. ``x[i:i+1,:]`` be too burdensome?
Yes.
> b. would ``rows`` and ``columns`` attributes that
> yielded matrics be an offsetting convenience?
I like the idea, from earlier in the thread, of row and col being
iterators for those time when you want to work on one column or row at
a time.
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