Excel Chart

Google for Excel, COM, macro, ...

You shouldn't have any trouble finding sample code (probably in VB or
VBA) to do what you want.

Alternately, any good book on advanced Excel or MS Office programming
should have the info you're looking for.

Regards

Dave M.

You can also try recording a macro of the steps you take to manually
produce the chart.

Record a macro making the chart full screen. Record a macro of it not
full screen. What's different in the two? Apply that to your Ruby code.