CODEWITHSUNDEEP
pythonarraysmatrixnumpy
user2509830
user2509830

Reputation: 93

Creating a Matrix in Python

I am trying to create a 100 by 100 matrix that will be populated with 1's and -1's(at random), and the diagonal of the matrix should be all zeros.

I am new to python and numpy.

Upvotes: 1

Views: 12066

Answers (3)

sundar
sundar

Reputation: 414

Here is a simple python line to create a 2D matrix - 100X100:

  yourmatrix = [[0 for x in xrange(100)] for x in xrange(100)]

Upvotes: 0

Saullo G. P. Castro
Saullo G. P. Castro

Reputation: 58995

To create the matrix with ones:

a = numpy.ones( (100,100) )

To create the random matrix:

a = numpy.random.random( (100,100) ) # by default between zero and one

To set all the diagonals to zero:

numpy.fill_diagonal(a, 0)

Upvotes: 3

Brian
Brian

Reputation: 3131

As an alternative, just using list comprehension and random:

from random import randint
x = [1,-1]
my_matrix = [[x[randint(0,1)] if i!=j else 0 for i in range(100)] for j in range(100)]

This will give you the random choice between -1 and 1 with 0 for the diagonal. You can embed this in a function to give you a matrix of NxN size as follows:

from random import randint
def make_matrix(n):
    x = [-1,1]
    return [[x[randint(0,1)] if i!=j else 0 for i in range(n)] for j in range(n)]

Upvotes: 0

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