Numpy create boolean array from checking if an array index equal a letter

Question

I have a numpy array of letters 'x' and 'y'. How do I make a boolean array for this that returns true if index == 'x' and false otherwise?

In addition to John1024's answer, have a look at the functions in numpy.char for vectorized versions of things like upper, isspace, etc: docs.scipy.org/doc/numpy/reference/routines.char.html — Joe Kington
– Joe Kington, Commented Mar 17, 2015 at 1:58

John1024 · Accepted Answer · 2015-03-17 01:17:53Z

1

In [1]: import numpy as np

In [2]: a = np.array(['x', 'y', 'y', 'x', 'y'])

In [3]: a == 'x'
Out[3]: array([ True, False, False,  True, False], dtype=bool)

answered Mar 17, 2015 at 1:17

John1024

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Alex Reynolds · Accepted Answer · 2023-07-17 15:22:43Z

0

A more general approach, useful for multiple letter conditions:

base_mask = lambda x: x == 'A' or x == 'a' or x == 'T' or x == 't'
vec_base_mask = np.vectorize(base_mask)
seq = 'TCTATcgGGa'
a = np.array([*seq])
masked_a = vec_base_mask(a)

# >>> masked_a
# array([ True, False,  True,  True,  True, False, False, False, False,
#         True])

answered Jul 17, 2023 at 15:22

Alex Reynolds

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