#
# "sharpen" filter
#

set sample 300
set yrange [-15:5]
set xrange [-10:2]
set grid x
set xtics 1
set key right center title "lgamma(x)"  samplen 0

set multiplot layout 2,1 title "Effect of 'sharpen' filter"
plot lgamma(x) title "no filters"
if (GPVAL_VERSION >= 6.0) {
    plot lgamma(x) sharpen title "  sharpen"
} else {
    set label 1 center at graph 0.5, 0.5 "This copy of gnuplot does not support 'sharpen'"
    unset key; plot NaN
}
unset multiplot


Click here for minimal script to generate this plot