I'v got two numpy arrays. The first array contains some zeros (which are distributed randomly over the length of the array), which I would like to remove.
My issue is that I would also like to remove the entries of the second array at the index positions where the first array elements are zero.
I only came up with a very cumbersome for-loop. Does anyone have an "elegant" method for doing this?
Thx!
Is it what you want? I am a NumPy newbie.
In [1]: import numpy as np
In [2]: a = np.array([1,2,0,3,0,4])
In [3]: b = np.array([1,2,3,4,5,6])
In [4]: b[np.where(a)]
Out[4]: array([1, 2, 4, 6])
In [5]: np.where(a)
Out[5]: (array([0, 1, 3, 5]),)
In [6]: a[np.where(a)]
Out[6]: array([1, 2, 3, 4])
You can use boolean indexing. x!=0 gives you a boolean array with True where x!=0 false where x==0. If you index either x or y with this array (ie x_nozeros=x[x!=0]) then you will get only the elements where x!=0. eg:
In [1]: import numpy as np
In [2]: x = np.array([1,2,0,3,0,4])
In [3]: y = np.arange(1,7)
In [4]: indx = x!=0
In [5]: x_nozeros = x[indx]
In [6]: y_nozeros = y[indx]
In [7]: x_nozeros
Out[7]: array([1, 2, 3, 4])
In [8]: y_nozeros
Out[8]: array([1, 2, 4, 6])
