How to tweak automatic-tics-number in gnuplot?

Question

It is helpful that gnuplot automatically picks up reasonably good x/y-range, and x/y-tics number (say approx 5 as attached figure).

However, I sometimes would like to increase/decrease the number of tics.

Of course, changing number of tics is easy. The thing I would like to do is, to take the advantage of this gnuplot "automatic tics selecting", but tweaking the approx number of tics. Is there any way to deal with this?

Thank you!

Answer 1

OK, now I see your point. Especially in multiplots or when the graphs are getting small relative to the size of the tic labels there are too many tics.

Find below a workaround which seems to work in the demonstrated cases. If it works nicely all the time you need to test. The disadvantage is that you have to plot first to a dummy table in order to get the range which gnuplot puts into the GPVAL_... variables and then replot again.

In the graph below the first row is gnuplot auto-tic, the second row the attempt for semi-auto-approximate-tic. Maybe it is a starting point for further tweaking.

Script:

### set approximate number of tics with "nice" intervals
reset session

round(n) = gprintf("%.0e",n)
# alternatively with less approximate tics: 
# round(n) = gprintf("%.0e",n) + sgn(n)*10**gprintf("%T",n)

approxTicsX(n) = round((GPVAL_X_MAX - GPVAL_X_MIN)/n)
approxTicsY(n) = round((GPVAL_Y_MAX - GPVAL_Y_MIN)/n)

set multiplot layout 2,3 rowsfirst

    ### with gnuplot auto-tics
    set xrange [-10:10]
    plot x

    set xrange [-100:100]
    plot x**2

    set xrange [-90:90]
    plot x

    ### now with semi-auto tics
    set style line 1 lc rgb "red"
    set xrange [-10:10]
    set table $Dummy
        plot x ls 1
    unset table
    set xtics approxTicsX(5)
    set ytics approxTicsY(5)
    replot

    set xrange [-100:100]
    set table $Dummy
        plot x**2 ls 1
    unset table
    set xtics approxTicsX(5)
    set ytics approxTicsY(5)
    replot

    set xrange [-90:90]
    set table $Dummy
        plot x ls 1
    unset table
    set xtics approxTicsX(5)
    set ytics approxTicsY(5)
    replot

unset multiplot
### end of script

Result: