multiple graphs in 1 plot

Hi,

I'm trying to get more than 1 graph in a plot, but so far I only get the 
last one visible.

function [y1,y2] = test(x)
y1 = x + 4
plot(y1,'1')
y2 = 2*x.^2 + 3*x + 2
plot(y2,'2')
endfunction

I can see y1 for a very short time. Then y2 is plotted and y1 isn't 
visible anymore. Any solution to this?

Thanks,

Huub