Hello, I want to use TableForm and TableHeadings for a batter data visualization. I have first used it in a matrix with only numbers and symbols, and it worked just fine. I tried to use it again with another matrix, but this one have Sum in it, and a f[i] in that sum,and that's the only difference I can see between the two cases. But when I used TableHeadings in that second case, I haven't got the lines separating the headings from the data.. Does anyone know why this happens? :( Thanks already for the help!