Numpy merging arrays

Question

I have two arrays

 a = np.array[1,18,3,13,6,45,45]
 b= np.array [8,13,6,45,45]

after doing some matching exercises I have a list, such as:

[3,1,4]

first and second number of the list are zero based. the third number is not. the list stands for

start position of first array
start position of second array
how many numbers rows to retrieve

so for this example the result would be

Both starting points of the array and then get 4 rows after that.

How can I merge my two arrays using my matchlist?

EDIT This is the matchlist that I am using:

matchlist2 = []

matchlist2.append([3,1,4])
matchlist2.append([9,7,731])
matchlist2.append([766,762,19])
matchlist2.append([800,796,57])
matchlist2.append([867,862,88])
matchlist2.append([960,955,468])
matchlist2.append([1432,1427,65])
matchlist2.append([1523,1518,341])
matchlist2.append([1873,1868,32])
matchlist2.append([1923,1916,82])
matchlist2.append([2011,2004,699])
matchlist2.append([2716,2707,902])
matchlist2.append([3628,3617,247])
matchlist2.append([3923,391,378])
matchlist2.append([4306,4292,5])

Given, l = [3,1,4] : a[l[0]:l[0]+l[2]] , b[l[1]:l[1]+l[2]]? — Divakar
– Divakar, Commented Dec 14, 2017 at 22:17
What data structure would your result have to be in? A 2 column array? Or would you need a list of tuples? — Saravana Kumar
– Saravana Kumar, Commented Dec 14, 2017 at 22:17
@Saravana Kumar , it would have to be in a 2 column array thanks! — yanci
– yanci, Commented Dec 14, 2017 at 22:22

Saravana Kumar · Accepted Answer · 2017-12-18 21:57:35Z

1

I would do it something like this:

result = np.array([[[a[ind[0]],b[ind[1]]] for ind in zip(range(ml[0],ml[0]+ml[2]),range(ml[1],ml[1]+ml[2]))] for ml in matchlist2])

Edit: Divakar's solution is actually much more elegant. If you just zip it up you'd get what you need.

result = [list(zip(a[l[0]:l[0]+l[2]],b[l[1]:l[1]+l[2]])) for l in matchlist2]

edited Dec 18, 2017 at 21:57

answered Dec 14, 2017 at 22:27

Saravana Kumar

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10 Comments

yanci Over a year ago

I am getting this error: TypeError: slice indices must be integers or None or have an index method. I may just be doing something wrong though

Saravana Kumar Over a year ago

Well can you see what your matchlist looks like? For some reason python thinks the elements of your matchlist are not integers.

yanci Over a year ago

I included the matchlist that I am using

Saravana Kumar Over a year ago

Alright so your matchlist is actually a 2D array. Let me edit my answer.

yanci Over a year ago

How do you display the contents of the merged list? I only see "<zip object at 0x......"

|

halfer · Accepted Answer · 2018-03-31 00:07:30Z

0

This is what you need:

a = np.array([1,18,3,13,6,45,45])
b = np.array([8,13,6,45,45])

look = [3,1,4]
first, second, step = look
c = np.array(zip(a[first:first+step],b[second:second+step]))
c
#[[13 13 
# [ 6  6
# [45 45
# [45 45]]

edited Mar 31, 2018 at 0:07

halfer

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answered Dec 18, 2017 at 16:14

zipa

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1 Comment

yanci Over a year ago

I am using spyder, and when I get 'object arrays are currently not supported'

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