If a graph is already visible can I still plot individual points onto it? If so how do I do this.
Furthemore, how do I actually plot individual (x,y) points? I have only encountered either plotting from a .dat file or by plotting a function.
Thanks in advance,
No to the first question. You have to "replot" the graph with additional data, unless you were in multiplot mode already --- but if you were, you wouldn't be asking this question ;-)
You don't "plot" individual points, but you can plot inline data files. See "help plot datafile special"
Do you know of any other graphing library similar to gnuplot where it would be possible to plot data on it onto a visible graph once it becomes available?
There can't be a "libary like gnuplot", because gnuplot is not a library (yet).
But you may want to check out GNU plotutils.