How to fill in a zeroes matrix using data from a separate array?

I am trying to work out how to fill in a matrix of zeroes to represent precedence requirements.   I have a 40x40 matrix of zeroes, and each collumn and row represent the tasks 1:40. I also have a 121x2 matrix with the precedent requirements. This is such that if a task needs to be completed before a different task can start, the first task is listed in collumn one and the second in collumn two.   I want to represent this in the form of having a matrix of 1s and 0s where a 1 is placed in row 1 collumn 2, it shows that task 2 relys on task one having happened. If there is a 0 there is no precedence requirement.   Is there a way i can take my 121x2 matrix and populate the 40x40 matrix accordingly? I assume it will be through a loop of reading each like of the 121x2 matrix and populating the 40x40 in this way but i wouldn't know how to approach the code for this.