Try something like this —
S = 10*sin(diag(0:19))
S = 20×20
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 8.4147 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 9.0930 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 1.4112 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 -7.5680 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 -9.5892 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 -2.7942 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 6.5699 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 9.8936 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 4.1212 0 0 0 0 0 0 0 0 0 0
.