gnuplot: plots not showing up

[Huub van Niekerk]

Hi,

After loading a mat file, I'm trying to plot a figure like this:

pear = peri_unknown([10:15]);
apple = peri_unknown([1:10, 15:20]);
mean_pear = mean(pear)
mean_apple = mean(apple)
mean_all = mean(peri_unknown)
plot(normpdf(5.5:0.1:8, mean(apple),std(apple)));

However, while I don't get an error and the terminal-title shows "Terminal - gnuplot-4.2.5--209x49" there's not plot visible. Any idea what I may do wrong?
Other question: how can I give a specific colour to the graph? I've looked at the "help plot" and tried in the beginning of plot and in the end, but all I get is errors.

Thank you.