The world famous 2D/3D plotting software Gnuplot has a function that you can plot a data with a line and some of the points on the line (after version 4 or so).
plot "data.txt" using 1:2 w lp pi 20
This plots column 1 and 2 data for x and y axes with lines and points, while the points appear once in every 20 data points.
However, ususally you do not know total number of the data contained in a file and just want 20 points appearing on the line drawn from the left end to the right end of the plot.
For this purpose, I wrote a patch (many years ago :-) containing a function called "pointnumber" that specifies the total number of points appearing on a line.
This works like this:
plot "data.txt" using 1:2 with linespoints pointnumber 20
plot "data.txt" using 1:2 w lp pn 20
Then, the line is drawn using all the data points, while only 20 points appear along the line.
The patch is available for download at the following link.
Enjoy plotting :-)
- Correction: Nov. 19, 2016: "set pointnumber .." does not work. "pointnumber" option is applicable only in the "plot ..." command as same as the "pointinterval".
- Patched and compiled binaries (executables) are also available for Linux Mint (*.deb) and Windows (*.zip) at the download link above. The windows version is not an installer. Extract in any place and add the path of "gnuplot/bin" to the $PATH environmental variable, or put the link of wgnuplot.exe to the start menu.
- Correction of the patch: Jan. 28, 2017: now it does not use random number to fluctuate the offset of the first drawn point.
- Correction of the patch: Jan. 30, 2017: I changed the algorithm for the shifting of the starting offset of the points; now, it looks much better, while the number of points actually drawn can change by missing a point the the edge; it should be no problem; also, fixes were made for consistency in lines/points style handling. (Thanks to comments by Ethan!)
adding an image to make this page look a bit better :-)