Question about scientific calculations in Python

[Martin Kaufmann]

On Tue, 12 Mar 2002 23:04:19 -0600, "Jason Orendorff"
<jason at jorendorff.com> wrote:

Thanks a lot! This is really an amazingly helpful reply. This group is
a good example for how Usenet should ideally be!

>I'm going to attempt to explain how you can do this with Numeric
>Python, but you'll have to understand I have no clue what I'm
>doing scientifically.

It doesn't matter. You got the point of my program.

>So in particular I'm assuming that "atoms" is a scalar, say atoms=1000.
>I also don't really know why you're using s_vector[1:] ... intentionally
>omitting the zeroth data point for some reason...?

This is just because the program that calculates the scattering
factors (which I didn't write myself) starts too low for our
purpose...

>Anyway, here's an interactive session that implements the above
>algorithm using Numeric, with *no loops*.  Or rather, the loops are all
>hidden away where you don't have to worry about them.  (They should
>run faster, too.)

[NumPy Tutorial for Dummies snipped...]

Thanks! I can't claim that I understood every line, but with this code
and the NumPy documentation I will make a huge step forward.

>The histogram version is up to you.  :)

As an exercise for the reader...

>Numeric lets you mix arrays and scalars randomly and it happily
>distributes multiplication and so forth.  So the resulting code
>looks a bit more like the original formulas.  Some folks like that.
>But if you don't, you can always code this in C and it'll be faster
>still.  It won't take very long to learn C.  The real problem is
>that C programs can be very difficult and time-consuming to debug.

If I write anything at all in C, it will only be a small part. Python
is so much more fun!

Many Thanks,

Martin