[Numpy-discussion] element wise help

josef.pktd@gmai... josef.pktd@gmai...
Thu May 7 12:37:40 CDT 2009


On Thu, May 7, 2009 at 1:08 PM, Chris Colbert <sccolbert@gmail.com> wrote:
> let me just post my code:
>
> t is the time array and n is also an array.
>
> For every value of time t, these operations are performed on the entire
> array n. Then, n is summed to a scalar which represents the system response
> at time t.
>
> I would like to eliminate this for loop if possible.
>
> Chris
>
> #### code ####
>
> b = 4.7
> f = []
> n = arange(1, N+1, 1)
>
> for t in timearray:
>         arg1 = {'S': ((b/t) + (1J*n*pi/t))}
>         exec('from numpy import *', arg1)
>         tempval = eval(transform, arg1)*((-1)**n)
>         rsum = tempval.real.sum()
>         arg2 = {'S': b/t}
>         exec('from numpy import *', arg2)
>         tempval2 = eval(transform, arg2)*0.5
>         fval = (exp(b) / t) * (tempval2 + rsum)
>         f.append(fval)
>
>
> #### /code #####
>

I don't understand what the exec statements are doing, I never use it.
what is transform?
Can you use regular functions instead or is there a special reason for
the exec and eval?

In these expressions ((b/t) + (1J*n*pi/t)),  (exp(b) / t)
broadcasting can be used.

Whats the size of t and n?

Josef


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