I've used this approach before, and in fact, for most purposes it is as
"valid" as using a surface chart. Many times the different dimensions are
not physical dimensions, and often they are not continuous but discrete, so
using separate lines on a line or XY chart is completely appropriate, and
has the benefit of being easier to read.

"Del Cotter" wrote in message
...
On Fri, 16 May 2008, in microsoft.public.excel.charting,
Jon Peltier said:

is it even possible to draw more than one surface on the same plot?

No

Not on the same Excel Surface Chart type, but it's easy on the
ever-versatile Scatter Chart. Here's the equation plotted for one surface
in the x-z plane:

http://www.branta.demon.co.uk/excel/eqsurf.xls

I wouldn't normally show the y=1, y=2 lines etc., as they're basically
vertical gridlines, but I thought they gave the surface a pleasantly
net-like quality. Adding a second surface is trivial, and adding the line
of intersection between two surfaces is a matter of calculation.

With a bit more calculation it should be possible to arrange to show only
the surface that is highest (or lowest) in a given region, to give a
"phase diagram" of lowest price suppliers for a given combination of x and
y. In other words it would be a surface graph of lowest z, plotted on the
x-y plane.

--
Del Cotter
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