Finding indices of repeated values in numpy array

Question

Here's my problem: I'm dealing with output from different receivers, and they are listed by number in column 0 of my array. I'm trying to find the indices that correspond to certain receiver values that show up. For my code below, I was trying to find all indices that had a value of 6.

My problem is that for the output (print) I'm only getting [ ], as if there are no indices that correspond to values for receiver 6. I've seen the data file and know this to be incorrect. The data text file is a 4x22000ish array. Any help would be greatly appreciated. thanks.

from numpy import *

data = loadtxt("/home/***")
s,t,q = data[:,0], data[:,2], data[:,3]                         
t,q = loadtxt("/home/***", usecols = (2,3), unpack=True)

indices = []
for index, value in enumerate(data[:,0]):
    if value == '6':
        indices.append(index)

print indices

gggg · Accepted Answer · 2013-07-30 23:42:07Z

1

numpy.nonzero(data[:,0]==6)[0]

data[:,0]==6 returns an array of booleans, 1 when the condition is true, 0 when it is false

numpy.nonzero returns the index of nonzero elements inside of a container

you may also be interested to know that you can do things like

data[data[:,0]==6,2]

to grab all the elements from the 2nd column when the first column is zero

answered Jul 30, 2013 at 23:42

gggg

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