#
# Illustrate use of concave hull to demarcate overlapping clusters
#
if (!strstrt(GPVAL_COMPILE_OPTIONS, "+CHI_SHAPES")) {
    print "This copy of gnuplot does not support concave hulls"
    exit  # return to caller
}

set title "{/:Bold RA Fisher's iris data set}"
set title offset 0, -2

species(name) = strstrt(name,"setosa") ? 1 \
              : strstrt(name,"versicolor") ? 2 \
              : strstrt(name,"virginica") ? 3 \
              : 0

set datafile separator comma
set datafile columnhead

set key title "Iris Species" font ":Bold"
set key outside top right offset screen -0.3, -.2
set key invert reverse Left

set border 3
set tics nomirror

set offset 0.5, 0.5, 0.5, 0.5
set xtics rangelimit
set ytics rangelimit
set xlabel "Sepal Width"
set ylabel "Petal Length"
set size square

plot 'iris.dat' using 2:3:(species(strcol(5))) with points lc variable notitle, \
    keyentry with point pt 7 lc species("setosa") title "setosa", \
    keyentry with point pt 7 lc species("versicolor") title "versicolor", \
    keyentry with point pt 7 lc species("virginica") title "virginica"


Click here for minimal script to generate this plot

set title '{/:Bold Concave Hull       chi\_length = 1.5 expand 0.1}'
set title offset 0, -2

set style fill transparent solid 0.3

chi_length = 1.5

plot for [s=1:3] \
    'iris.dat' using (species(strcol(5)) == s ? $2 : NaN) : 3 \
    concavehull smooth path expand 0.1 with polygon lc s notitle, \
    \
    '' using 2:3:(species(strcol(5))) with points pt 12 lc variable notitle, \
    \
    keyentry with ellipse lc species("setosa") title "setosa", \
    keyentry with ellipse lc species("versicolor") title "versicolor", \
    keyentry with ellipse lc species("virginica") title "virginica"


Click here for minimal script to generate this plot