I have a problem I don't know how to describe it so you understand. 
I am going to give an example.
Let's say we have this array (B) in python:

```
[[ 1  1]
 [ 7 11]
 [1 20]
 [20 1]
 [26 11]
 [31 11]]

```

The first column represents the users. The second the tags.
Now, I want to create a matrix who will have "1s" where edges exist otherwise "0s".
We have 5 and 4 different users and tags respectevily, that is a 6\*5 matrix..
If I write:

```
zero = np.zeros((6,5,).astype(int) #it needs one more row and column
for line in B:
 if line[2]:
    zero[line[0],line[1]] = 1

```

the error is:

```
   zero[line[0],line[1]] = 1

```

IndexError: index 7 is out of bounds for axis 0 with size 7

Ok, how can I make the combination between two matrices because I want the element "31" to be the fifth row and element "11" the fourth column.