I have an array of four rows A = array([[-1, -1, -1, -1], [-1, -1, 1, 2], [-1, -1, 1, 1], [2, 1, -1, 2]])
. In each row there are 4
numbers. How do I remove row#3
and row#4
? In row#3
and row#4
, 1
and 2
appear more than once respectively.
Is there a faster way to do it for arbitrary number of rows and columns? The main aim is to remove those rows where a non negative number appear more than once.
You can use something like this: first create dictionary of occurrences of each value in the sub arrays using np.unique and only keep arrays where no positive number appears more than once.
A = np.array([[-1, -1, -1, -1], [-1, -1, 1, 2], [-1, -1, 1, 1], [2, 1, -1, 2]])
new_array = []
# loop through each array
for array in A:
# Get a dictionary of the counts of each value
unique, counts = np.unique(array, return_counts=True)
counts = dict(zip(unique, counts))
# Find the number of occurences of postive numbers
positive_occurences = [value for key, value in counts.items() if key > 0]
# Append to new_array if no positive number appears more than once
if any(y > 1 for y in positive_occurences):
continue
else:
new_array.append(array)
new_array = np.array(new_array)
this returns:
array([[-1, -1, -1, -1],
[-1, -1, 1, 2]])
My fully-vectorized approach:
import numpy as np
a = np.array([[-1, -1, -1, -1], [-1, -1, 1, 2], [-1, -1, 1, 1], [2, 1, -1, 2]])
# sort each row
b = np.sort(a)
# mark positive duplicates
drop = np.any((b[:,1:]>0) & (b[:,1:] == b[:,:-1]), axis=1)
# drop
aa = a[~drop, :]
Output:
array([[-1, -1, -1, -1],
[-1, -1, 1, 2]])
I modified also to store the indices:
A = np.array([[-1, -1, -1, -1], [-1, -1, 1, 2], [-1, -1, 1, 1], [2, 1, -1, 2]])
new_array = []
**indiceStore = np.array([])**
# loop through each array
for array in A:
# Get a dictionary of the counts of each value
unique, counts = np.unique(array, return_counts=True)
counts = dict(zip(unique, counts))
# Find the number of occurences of postive numbers
positive_occurences = [value for key, value in counts.items() if key > 0]
# Append to new_array if no positive number appears more than once
if any(y > 1 for y in positive_occurences):
**indiceStore = np.append(indiceStore, int(array))**
continue
else:
new_array.append(array)
new_array = np.array(new_array)
Let me kniow if this is right.
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