On Wed, Nov 25, 2009 at 10:07 PM, shaunc <[email protected]> wrote:
> Hello!
>
> I am new to sage -- but an experienced python user.
> I have successfully installed sage (except for plotting on mac 10.6 --
> but I understand that's being worked on).
>
> I wanted to build a vector of random numbers, and did the following:
>
> sage: import random
> sage: import numpy as N
> sage: u = random.uniform
> sage: N.fromfunction( lambda i: u( 0., 1. ), ( 3, ) )
> 0.513723977031280
>
> !! why not an array?
>
> However, the following works slightly differently....
>
> sage: N.fromfunction( lambda i: u( 0.*i, 1. ), ( 3, ) )
> array([ 0.65361094, 0.65361094, 0.65361094])
>
> It would seem that sage is trying to optimize the expression... (but
> not very systematically, as the difference of the answers shows).
>
> Even stranger:
> sage: N.fromfunction( ( lambda i: u( 0, 1.*i ) ), ( 3, ) )
> array([ 0. , 0.92293102, 1.84586204])
>
> Here it seems to have called u once and then scaled the result???
>
> Can I turn this off -- it seems likely to cause bugs?! And in any
> case, why doesn't it give me an array of 3 constants in the first
> case?
These seem to all be NumPy questions. You might also want to post
to the NumPy mailing list:
http://www.scipy.org/Mailing_Lists
William
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