I want to plot a filled circle in Gnuplot, but with transparency changing with the distance to the center of the circle, i.e. a transparency gradient (solid near to the center, and transparent near to the radius of circle).
Is there any way of doing this in Gnuplot?
Thank you in advance!
One option would be to define a custom function describing the gradient (e.g., a Gaussian) and then use pm3d map to visualize it:
set terminal pngcairo size 400,400
set output 'fig.png'
unset border
unset colorbox
unset xtics
unset ytics
set pm3d map
#force the plot to occupy the entire canvas
set lmargin at screen 0
set rmargin at screen 1
set tmargin at screen 1
set bmargin at screen 0
set isosamples 100,100
#specify custom palette
set palette model RGB
set palette defined ( 0 "white", 1 "royalblue" )
set xr [-10:10]
set yr [-10:10]
#a Gaussian might be a reasonable choice
splot exp(-0.2*(x*x+y*y))
This then produces:
Another choice of the defining function might be:
set xr [-pi:pi]
set yr [-pi:pi]
fn(r) = (r>(pi/2))?0:(cos(r))
splot fn(sqrt(x*x+y*y))
This yields:
Try this:
set xrange [0:10]
set yrange [0:10]
do for [i=1:100] {
set style fill transparent solid i/100. noborder
set object circle at 5,5 radius 1.-i/100. fc rgb 'blue'
}
plot -1
Not all terminals support transparency; see help transparent. I made this with the terminal x11.
