To test certain modeling constructs it may be useful to generate some random data. In GAMS this is usually done through something like:
a(i,j,k) = uniform(-100,100);
When we want to have a sparse data set we can use the following:
a(i,j,k) = uniform(-100,100)$(uniform(0,1)<0.1);
i.e. with probability 0.1 generate an entry in A with a random value between -100 and 100.
This can also be written as:
a(i,j,k)$(uniform(0,1)<0.1) = uniform(-100,100);
For very large, very sparse structures it may be even better to generate a random sparsity pattern first. E.g. using something like: