CODEWITHSUNDEEP
pythonnumpy
Dario
Dario

Reputation: 331

Slice array using other array

I have two arrays of the same length that contain elements from 0 to 1. For example:

x = np.linspace(0,1,100)
y = np.random.permutation(x)

I grouped the elements of x in bins of width 0.1:

bins = np.arange(0,1,0.1)
x_bin = []
for i in range(1,10):
    x_bin.append(x[np.digitize(x,bins)==i])

Now I would like to slice y in groups which have the same lengths of the arrays in x_bin.

How can I do that?

A possible way is:

y0 = y[0:len(x_bin[0])]

and so on, but it is not very elegant.

Upvotes: 0

Views: 83

Answers (2)

ifumho
ifumho

Reputation: 141

This may be what you want to use as a more elegant solution than using loops:

l = [len(x) for x in x_bin]  # get bin lengths
split_indices = np.cumsum(l)  # sum up lengths for correct split indices
y_split = np.split(y, split_indices)

I got the array lengths via list comprehension and then splitted the np array using the gathered indices. This can be shortened to a single python instruction, but it is much easier to read this way.

Upvotes: 1

Almog-at-Nailo
Almog-at-Nailo

Reputation: 1182

A possible way is:

y0 = y[0:len(x_bin[0])]

and so on, but it is not very elegant.

instead of using y0 = ... y1 = ... you can make a list of slices:

slices = []
for n in len(y):
    slices.append(y[n:len(x_bin[0])])

(this might be wrong, but the principle is there)

instead of haveing y0 y1 and so on, you will have slices[0], slices[1] and so on

Upvotes: 0

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