index masked element Array

Question

I have a array

z = np.random.random((10,10))  --> two dimensions

with a mask

y,x=np.mgrid[slice(0,61, 1),slice(0,106, 1)] 

sorted = np.sort(z,axis=None)
mask = ma.masked_inside(z,sorted[10],sorted[-10])

mask is Array masked inside only the 10 min element and 10 max inside with a mask TRUE. I need the index position to put x,y in the annotate, but only like create element that is masked

I will like return mask elements masked and the index position in the axis of all the elements to create a automatic annotates objects

 ax.annotate(str(j)+" Altura",xy=(i,j))

Hooked · Accepted Answer · 2014-02-20 15:19:16Z

3

To return the "index position", use np.where on the mask. For example:

import numpy as np
A = np.array([[2,7,9],[9,1,4],[8,7,2]])
idx = A<3 # The mask

print np.where(idx)
print zip(*np.where(idx))

Gives:

(array([0, 1, 2]), array([0, 1, 2]))
[(0, 0), (1, 1), (2, 2)]

that is, the locations where A<3. I find zipping over the elements and packaging them as a list of tuples useful, but use the first representation to index them back from the original array.

answered Feb 20, 2014 at 15:19

Hooked

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3 Comments

virtualsets Over a year ago

Thank you. And if I have the array masked in this moment. this is my final array masked _f_data= np.ma.masked_array(np.around(z, decimals=4, out=None),~_c)

Hooked Over a year ago

@virtualsets I'm not sure I understand what you're asking in that comment.

virtualsets Over a year ago

I not understand your mask, my mask is ~c and is the joint of two another mask. I have one mask ~c and one array z

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