Coupling matrix element, variance

We add to A another matrix, S, whose elements are drawn from a normal probability distribution N(0, with zero mean and a variance denoted by cr. A fraction /of the elements of the matrix A will be populated in this way the rest will be zero, so 0 0, the matrix S is very sparse, and different variables, x, are relatively uncoupled by the perturbations. Likewise, as n increases, so the system becomes larger, with more and more components of the vectors coming into play. Finally, as the variance of the stochastic perturbations, cr, increases, so the broader is the influence of random effects from one interaction pathway to others. Thus, the complex system is now turned into the stochastic differential equation... 

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