Plotting JONSWAP spectrum, nothing happens

Hi,

I am trying to plot a JONSWAP spectrum with a code, which can be seen here: http://www.maths.lth.se/matstat/wafo/documentation/wafodoc/wafo/spec/jonswap.html

However, when I run the code and use the default values and use plotflag=1, nothing happens. I'm a beginner in matlab, so I might be missing something essential. Could anyone help me out?

Thanks.