Numpy method to return the index of the occurrence of an array within an array of arrays

Question

I have an array of arrays that represents a set of unique colour values:

[[0.         0.         0.        ]
 [0.         0.         1.        ]
 [0.         1.         1.        ]
 [0.5019608  0.5019608  0.5019608 ]
 [0.64705884 0.16470589 0.16470589]
 [0.9607843  0.9607843  0.8627451 ]
 [1.         0.         0.        ]
 [1.         0.84313726 0.        ]
 [1.         1.         0.        ]
 [1.         1.         1.        ]]

And another numpy array that represents one of the colours:

[0.9607843  0.9607843  0.8627451 ]

I need a function to find the index where the colour array occurs in the set of colours, i.e. the function should return 5 for the arrays above.

errno98 · Accepted Answer · 2019-07-17 13:42:29Z

1

numpy.where() returns you the exact positions in the array for values of given condition. So here, it would be as following (denoting big array as arr1, and the sought vector as arr2:

np.where(np.all(arr1 == arr2, axis=1))

Which then returns array of row indexes of sought rows.

edited Jul 17, 2019 at 13:42

answered Jul 17, 2019 at 13:37

errno98

3322 silver badges14 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Zachary Oldham · Accepted Answer · 2019-07-17 13:12:21Z

Assuming that this is a relatively short list of colors (<1000), the simplest thing to do is probably just iterate over the list and compare each element of the sub-array.

color_list = ...
color_index = -1
target_color = [0.9607843, 0.9607843, 0.8627451]
for i in range(0, len(color_list)):
    cur_color = color_list[i]
    if (cur_color[0] == target_color[0] and cur_color[1] = target_color[1] and cur_color[2] = target_color[2]):
        color_index = i
        break

Collectives™ on Stack Overflow

Numpy method to return the index of the occurrence of an array within an array of arrays

2 Answers 2

Comments

Comments

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Related