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Re: [Gnuplot-info] Managing long/complicated plot commands?
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From: Bjorn B. <bjo...@gm...> - 2026-03-29 17:59:12
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Thank you Hernán for the further elaboration and the provided example! On Sun, Mar 29, 2026 at 7:53 PM Hernán De Angelis < var...@gm...> wrote: > Hi Bjorn, > > Yes, you understood correctly. Here you can see a very simple example > using Perl (but almost any other scripting language works): > > https://github.com/dhdeangelis/lcplot > > where the script downloads data, parses it in groups meant to be plotted > as different sets of points and chooses visually pleasant (for me) tic > parameters. This is written into a gnuplot script that is then passed as > argument for gnuplot. > > Arbitrarily complex gnuplot scripts can be efficiently written this way as > long as they respect gnuplot's syntax. Not shown in this example, but care > is necessary to adequately scape any eventual special character like "\", > "&". In Perl for example the sigils "$", "@", and "%" need to be escaped > when writing a gnuplot file using "\". Other precautions may apply in other > languages. > > Many script languages hace wrapper modules for gnuplot that may make life > easier. I personally prefer the above method though. > > Best of luck > > Hernán > > > Den 2026-03-29 kl. 19:32, skrev Bjorn Buckwalter: > > Hi Hernán and thanks for the suggestion. > > Do I understand correctly that you propose using a script written in > another language to generate the gnuplot script (the "configuration file")? > This may indeed be a good option, to generate a verbose and repetitive but > straight-forward gnuplot script. > > I will admit that I was rather happy to have my plotting infrastructure > being only self-contained gnuplot code, but I will seriously consider this. > > Thanks, > Bjorn > > > > > > On Sun, Mar 29, 2026 at 12:23 PM Hernán De Angelis < > var...@gm...> wrote: > >> You may already had this suggestion, as in using variables, but consider >> that given the length and complexity of your command, it is perhaps a >> better idea to use a script to do all steps from building your set of >> plot instructions, writing them to a configuration file, and then >> running the gnuplot command. I do this all the time to a good effect. >> >> /H. >> >> Den 2026-03-29 kl. 11:49, skrev Bjorn Buckwalter: >> > Thanks Jesper and Philpp. Jespers suggestion with variables can likely >> help >> > – I will try it! >> > >> > FYI here is an example plot command that fails: >> > >> > ``` >> > plot \ >> > 'world_110m.txt' using (lon($1)):(filter_lat($2)) with lines >> linecolor >> > "gray" notitle , \ >> > lat(0) with lines black dashtype 2 title "Equator" , \ >> > lat(66.6) with lines black dashtype 5 title "Arctic/Antarctic >> circle", \ >> > lat(-66.6) with lines black dashtype 5 notitle , \ >> > for [orbit in orbits] \ >> > 'data/Report'.orbit.'.txt' using (lon($7)):(filter_lat($6)) \ >> > with lines linecolor rgb next_color_t(n, 'cc') notitle, \ >> > for [orbit in orbits] \ >> > 'data/Report'.orbit.'.txt' using (lon($7)):($3 == 2030 ? >> > filter_lat($6) : NaN) \ >> > with lines linecolor rgb next_color(n) title orbit, \ >> > lat(lat1) black notitle # edge of plot >> > ``` >> > >> > There is A LOT going on there with various custom functions, etc. I >> tried >> > to make a minimal and “dependency-free” example but failed to reproduce >> the >> > behavior. I could maybe try harder. >> > >> > Here is in any case the error from gnuplot. The command has been >> > concatenated at all baskslashes except the last: >> > >> > ``` >> > plot 'world_110m.txt' using (lon($1)):(filter_lat($2)) with lines >> > linecolor "gray" notitle , lat(0) with lines black dashtype 2 title >> > "Equator" , lat(66.6) with lines black dashtype 5 title >> > "Arctic/Antarctic circle", lat(-66.6) with lines black dashtype 5 >> > notitle , for [orbit in orbits] 'data/Report'.orbit.'.txt' >> using >> > (lon($7)):(filter_lat($6)) with lines linecolor rgb >> next_color_t(n, >> > 'cc') notitle, for [orbit in orbits] >> 'data/Report'.orbit.'.txt' >> > using (lon($7)):($3 == 2030 ? filter_lat($6) : NaN) with lines >> > linecolor rgb next_color(n) title orbit, \ lat(lat1) black notitle # >> > edge of plot >> > >> > >> > >> > >> > >> > >> > >> > >> > ^ >> > "$plot_polar" line 15: invalid character \ >> > ``` >> > >> > There is nothing wrong with the backslash (no trailing spaces, etc.). >> > >> > If I change it as so (just shortening style definitions) it works: >> > >> > ``` >> > set style data lines >> > plot \ >> > 'world_110m.txt' using (lon($1)):(filter_lat($2)) lc "gray" >> notitle , \ >> > lat(0) black dt 2 title "Equator" , \ >> > lat(66.6) black dt 5 title "Arctic/Antarctic circle", \ >> > lat(-66.6) black dt 5 notitle , \ >> > for [orbit in orbits] \ >> > 'data/Report'.orbit.'.txt' using (lon($7)):(filter_lat($6)) \ >> > lc rgb next_color_t(n, 'cc') notitle, \ >> > for [orbit in orbits] \ >> > 'data/Report'.orbit.'.txt' using (lon($7)):($3 == 2030 ? >> > filter_lat($6) : NaN) \ >> > lc rgb next_color(n) title orbit, \ >> > lat(lat1) black notitle # edge of plot >> > ``` >> > >> > All I did was remove `with lines` (using `set style data lines` instead >> and >> > replace `linecolor` and `dashtype` with `lc` and `dt`, respectively. >> This >> > is why I say it seems to be somehow related to the length/number of >> > characters of a command. >> > >> > Thanks, >> > Bjorn >> > >> > >> > On Sun, Mar 29, 2026 at 5:28 AM Philipp K. Janert<ph...@ja...> >> wrote: >> > >> >> On Sat, 28 Mar 2026 22:13:40 +0100 >> >> Bjorn Buckwalter<bjo...@gm...> wrote: >> >> >> >>> HI all, >> >> How long (in characters) are the command lines that >> >> you are using? Mine frequently run long, and it has >> >> never been a problem. >> >> >> >> Is it possible that you have problems with embedded >> >> newlines, or that something goes awry if your command >> >> line runs into a new line in your terminal? >> >> >> >> Best, >> >> >> >> Ph. >> >> >> >>> I rather often run into a problem of my plot commands being too long, >> >>> typically resulting in a not-very-helpful error message such as: >> >>> >> >>> "$plot_polar" line 21: invalid character \ >> >>> >> >>> It took a lot of head scratching to realize the root of the problem. I >> >>> assume there are strong reasons for both the limitation on command >> >>> length and the poor error message. >> >>> >> >>> I cannot be the only one running into this problem. The situation >> >>> being what it is, what are the rest of you doing to manage when you >> >>> run up against this limit? Replacing `linecolor` with `lc`, etc, will >> >>> only get me so far and at the expense of readability. >> >>> >> >>> Many thanks, >> >>> Bjorn >> >>> >> >>> _______________________________________________ >> >>> gnuplot-info mailing list >> >>> gnu...@li... >> >>> Membership management via: >> >>> https://lists.sourceforge.net/lists/listinfo/gnuplot-info >> >> >> >> >> >> -- >> >> >> >> Philipp K. Janert >> >> www.janert.me >> >> >> >> >> >> _______________________________________________ >> >> gnuplot-info mailing list >> >> gnu...@li... >> >> Membership management via: >> >> https://lists.sourceforge.net/lists/listinfo/gnuplot-info >> >> >> > _______________________________________________ >> > gnuplot-info mailing list >> > gnu...@li... >> > Membership management via: >> https://lists.sourceforge.net/lists/listinfo/gnuplot-info >> >> _______________________________________________ >> gnuplot-info mailing list >> gnu...@li... >> Membership management via: >> https://lists.sourceforge.net/lists/listinfo/gnuplot-info >> > > |
