Thank you for answering.
I do agree that we could think of a lot of ways to represent data and that all of them would not be useful. Though I think the first thing you expect for initilizing a table (such as simplex table), is actually a usual matrix, ie a 2 dimentional table, ie a double pointer ('double **matrix' in my exemple), containing only values, no indices. I think it is not actually a representation of the data among others, it is the most intuitive one.
On the other hand, having three 1-dimentional table (2 for indices one for values), as curently done, may be very useful if the matrix has only few values differant from zero; but quite tedious to use in general case. Anyway, in my case adding the other method saved me time.