You can use a loop:
[m,n] = size(x);
legendText = cell(1, m);
for k = 1:m
legendText{k} = num2str(x(k, n));
end
[EDITED after comment]
x = rand(10, 5);
h = plot(x);
... Instert code from above here
legend(h, legendText);
See doc legend for more details and examples. Reading the documentation is very useful in Matlab, because this is (still, even with the new layout) the most productive documentation I've seen (except for the one of my hammer).
