> -Suppose I have some values in a file "x.txt" and the same number of
> values in another file "y.txt". How can I get gnuplot to plot the x's
> against the y's?
Not from inside gnuplot. You have to put them into the same file, at
plot '< paste x.txt y.txt'
will do, on a system that supports pipes.
> -Suppose I want to make a delay embedding, i.e. plot x values against
> former x values; I want each x(i) to be plotted against x(i-d), where
> d is the delay. How's it done?
Externally, but with different tools, in this case. Something like
plot '< tail +10 x.txt | paste - x.txt'