why won't the command semilogy work?

Whenever I try to create a figure using the command semilogy, the figure opens up but it's a blank page and it doesn't give me the graph.

[John D'Errico]

It works fine for us. Show an example where it fails for you, as we will not be able to reproduce whatever error you have made.

semilogy(1:10,rand(10))

[SOFIA]

figure(4)
semilogy (1:iter3N, abs(scarti3N), 'r-');

Unrecognized function or variable 'iter3N'.

hold on
semilogy (1:itertf3, abs(scartitf3), 'b-');
hold on
semilogy(1:iter3,abs(scarti3), 'm-');
title('convergence');
xlabel('iter');
ylabel('error');
legend('Newton-rhapson','tangente fissa','punto fisso');
hold off

[John D'Errico]

So your example where semilogy does not work, is the case of an undefined variable? You cannot plot something if it does not exist.

Unrecognized function or variable 'iter3N'.

Unless, of course, you have a beta copy of the mind reading toolbox. It was never officially released, as it is really buggy.

Seriously, READ THE ERROR MESSAGE. While you may think the variable iter3N exists somewhere, it is not in the workspace accessible to that call.