问题
I want to generate a gnuplot plot command programmatically, like:
plotline = sprintf("'datafile1.dat' using %d:3 with points, '%s' using %d:3 with points",i,targfile,i)
plot plotline
Where 'plotline' in the second line is expanded to produce and execute a full command like:
plot 'datafile1.dat' using 8:3 with points, 'datafile2.dat' using 8:3 with points
I want to do this in order to echo 'plotline' in the terminal and so be certain exactly what is being shown while cycling through a set of columns / datafiles / whatever inside a loop in a gnuplot script.
Is there / what is the syntax to do this, or can you suggest another approach to report the plot command as executed (without splitting into a plot command and a separate set of commands to report the current variable states).
Thanks!
回答1:
In order to construct such a plot command from some strings, you can use eval to execute the commands contained in a string:
plotline = 'x title "mytitle"'
eval('plot '.plotline)
Alternatively you can use set macros:
set macros
plotline = 'x title "mytitle"'
plot @plotline
This replaces @plotline with the content of the string variable plotline before executing the command. Using plot plotline interpretes the content of plotline as file name. Note, that as of version 4.6 macros don't work properly in loops, but eval works fine.
BTW: If you don't specify your own title, then the actual plot statement is written in the plot legend. But that can't be written to the terminal output.
来源：https://stackoverflow.com/questions/21233470/gnuplot-generate-plot-command-with-sprintf