I am using Gnuplot to successfully plot some time series data. However, the series are fairly dense (10,000\'s of samples in about 5 inches of space), and when I plot multiple s
Good news! This has been implemented in gnuplot. Example syntax is
plot x lw 10, -x lw 10 lc rgb "#77000000"
This will plot x as a red line and -x as a transparent black line (it looks gray). The first pair of two characters in the rgb specification define the alpha (transparency) channel ("#AARRGGBB"). The normal syntax ("#RRGGBB") still works.
If you want to make lines plotted for time series data, the answer is no (see discussion here). You can't set a line style to be transparent. Transparency only works for filling under curves, and it has to be printed to the right terminal type.
I ran into this problem myself recently, I hope this feature will be added in a future version of gnuplot.
This may be what you're looking for.