# set terminal pngcairo  enhanced font "arial,10" size 420, 300 
# set output 'transparent.4.png'
set clip two
set style fill  transparent pattern 4 border
set key title "Gaussian Distribution"
set key inside left top vertical Left reverse enhanced autotitles nobox
set key noinvert samplen 1 spacing 1 width 0 height 0 
set style function filledcurves y1=0
set title "Transparent pattern-filled curves" 
set rrange [ * : * ] noreverse nowriteback  # (currently [8.98847e+307:-8.98847e+307] )
set trange [ * : * ] noreverse nowriteback  # (currently [-5.00000:5.00000] )
set xrange [ -5.00000 : 5.00000 ] noreverse nowriteback
set x2range [ * : * ] noreverse nowriteback  # (currently [-5.00000:5.00000] )
set yrange [ 0.00000 : 1.00000 ] noreverse nowriteback
set y2range [ * : * ] noreverse nowriteback  # (currently [0.00000:1.00000] )
set cbrange [ * : * ] noreverse nowriteback  # (currently [8.98847e+307:-8.98847e+307] )
unset colorbox
Gauss(x,mu,sigma) = 1./(sigma*sqrt(2*pi)) * exp( -(x-mu)**2 / (2*sigma**2) )
d1(x) = Gauss(x, 0.5, 0.5)
d2(x) = Gauss(x,  2.,  1.)
d3(x) = Gauss(x, -1.,  2.)
GPFUN_Gauss = "Gauss(x,mu,sigma) = 1./(sigma*sqrt(2*pi)) * exp( -(x-mu)**2 / (2*sigma**2) )"
GPFUN_d1 = "d1(x) = Gauss(x, 0.5, 0.5)"
GPFUN_d2 = "d2(x) = Gauss(x,  2.,  1.)"
GPFUN_d3 = "d3(x) = Gauss(x, -1.,  2.)"
plot d1(x) fs solid 1.0 lc rgb "forest-green" title "μ =  0.5 σ = 0.5",      d2(x) lc rgb "gold" title "μ =  2.0 σ = 1.0",      d3(x) lc rgb "red" title "μ = -1.0 σ = 2.0"