I tried Google Docs to begin with, to find that it can't seem to do scatter graphs properly. And it's slow, because it's an AJAX application.
So I tried Apple Numbers, which can do scatter graphs, but can't put a line between the points. Also it's so slow! Unbelievable. Quad-processor machines shouldn't struggle like this with a simple spreadsheet.
Then I installed Microsoft Office 2008 and tried Excel. This is able to produce the graphs I want in theory, but it crashed when I tried. And, get this, it's even slower than Numbers!Another thing about Excel for Mac is, in the values for the maximum and minimum values of a graph axis, I can't paste or type anything other than decimal numbers. Which means I can't set the graph to start at "11/06/2008 10:00:00 AM", but I have to enter "39610.4166666667".
How is that useful?
What a crock of shit these spreadsheet programs are.
In the end I had to resort to using Excel 2003 for Windows at work, even though it produces the same ugly graphs it was making in 1995. To slightly un-uglify them, I printed to a PDF and rasterised that, to get the nice anti-aliasing.
Next time, I'll try something open-source like Gnuplot, which should make a good job of it.
Apple, Microsoft: You fail at making spreadsheet programs. Go and stand in the corner.