Re: [Matplotlib-users] Region within contour --> 2D array

slaps forehead...

Joe, you just won the "duh!" moment of the month award!

Cheers!
Ben Root



On Thu, Aug 28, 2014 at 10:18 PM, Joe Kington <jof...@gm...>
wrote:

> Why not just use boolean indexing?
>
> E.g. to find the region that falls between 5 and 10, do "(z >=5) & (z <=
> 10)":
>
> In [1]: import numpy as np
>
> In [2]: x, y = np.mgrid[-10:10, -10:10]
>
> In [3]: z = np.hypot(x, y)
>
> In [4]: result = (z >= 5) & (z <= 10)
>
> In [5]: result.astype(int)
> Out[5]:
> array([[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0],
>        [0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0],
>        [0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0],
>        [0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0],
>        [0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
>        [0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
>        [0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1],
>        [0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1],
>        [0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1],
>        [0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1],
>        [1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1],
>        [0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1],
>        [0, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1],
>        [0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1],
>        [0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1],
>        [0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
>        [0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0],
>        [0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0],
>        [0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0],
>        [0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0]])
>
> Cheers,
> -Joe
>
>
>
> On Thu, Aug 28, 2014 at 8:23 PM, Eric Firing <ef...@ha...> wrote:
>
>> On 2014/08/28, 3:02 AM, Matthew Czesarski wrote:
>> > Hi Matplotlib Users!
>> >
>> >
>> >
>> > I have some 2-d arrays, which i am displaying  with implot, and deriving
>> > contours for with contour.  Easy -  I'm just pulling them out of
>> > collections[0].get_paths() .
>> >
>> > However what's not easy is that I would like to recover a 1-0 or
>> > True-False array of the array values (pixels) that fall within the
>> > contours. Some line crossing algorithm/floodfill could do it, but I
>> > guess that matplotlib's fill() or contourf() must do this under the hood
>> > anyway. I've looked into the output both functions, but I don't see
>> > anything obvious..
>> >
>> > Does anybody know if there's an a way to pull out a such an array from
>> > matplotlib?   Any pointers are appreciated!
>>
>> Make an array of (x, y) pairs from the X and Y you use in your call to
>> contour, and then feed that array to the contains_points() method of
>> your contour Path.  This will give you the desired Boolean array for any
>> given Path; depending on what you want, you might need to combine arrays
>> for more than one Path.
>>
>> To get closed paths, I think you will want to use contourf, not contour.
>>
>> Eric
>>
>>
>>
>> >
>> > Cheers,
>> > Matt
>> >
>> >
>> >
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