Plotxy is a project mainly written in C, it's free.
Need to plot tens of millions of XY data-points and nothing works?
In the plotxy.codeproj/project.pbxproj the following edits were needed: 1:Project > $PROJECT_NAME > Search Paths > Header Search Paths: I added "/usr/X11/include/" 2: TARGETS > $PROJECT_NAME > Link Binary With Libraries: I added libpng.3.dylib