[cctbxbb] flex index

[Ralf Grosse-Kunstleve]

Hi Mona,

Try this:

from scitbx.array_family import flex
a=flex.double([1,4,5,7,5,6,6,1])
a.set_selected(a > 5, 5)
print list(a)

Or in smaller steps:

bool_selection = a > 5
assert bool_selection.size() == a.size()
print list(bool_selection)
a.set_selected(bool_selection, 5)
print list(a)

You can also call a.set_selected(bool_selection, b)
where b is an array with as many elements as you have True in the
bool_selection.

This kind of working with selections is very typical within cctbx/phenix.
If you look through our sources you'll find a lot of examples; in passing,
we have two types of selections, bool selections as above, and integer
selections. The latter are useful for permutations, e.g. to sort array
elements, or if you know you select only a small number of elements from a
large array. Let me know if you have more questions about selections and
I'll be happy to explain. (I guess one day I should write a "Working with
selections" tutorial.)

Ralf

On Tue, Oct 18, 2011 at 2:54 AM, Monarin Uervirojnangkoorn <
monarin at biochem.uni-luebeck.de> wrote:

> Hi,
>
> I'm using flex and 'd like to get an access to elements fall beyond/ below
> certain value. eg.
> a=[1,4,5,7,5,6,6,1]
> anything beyond 5 should be set to 5. (in matlab then a(a>5)=5;)
> if you could tell me how to do this quickly for flex, that would be great.
> for now i use loop and that is... pretty slow.
>
> many thanks.
> mona
>
>
>
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