Merge key entries in gnuplot

Question

I would like to plot data with lines and points with different colors. It seems to exist different solutions:

• https://stackoverflow.com/a/31887351/4373898 , ht

Answer 1

If your plot is not too complex, you could perhaps achieve this by playing with the spacing parameter of the legend. Setting spacing to -1 achieves that the labels/symbols overlap:

set terminal pngcairo enhanced
set output 'fig.png'

set xr [-pi/2:pi/2]
set yr [0:1]

set key at graph 0.95,graph 0.9 spacing -1

plot \
    cos(x) w l lc rgb 'dark-red' lw 2, \
    '-' w p lc rgb 'royalblue' pt 7 ps 2 t ' '
-1  0.540302
0   1
1   0.540302
e

which gives

However, the disadvantage is that the setting is in a sense global - should the plot contain more functions/data files, everything would overlap. In order to use this "method" in this particular case, it would be necessary to invoke multiplot and create the keys separately.