set terminal svg name 'IQ_curve' size 600,480 font ',10' rounded
set output 'IQ_curve.svg'

mu    = 100.0
sigma = 15.0
from  = 55
to    = 145

# Normal distribution:
# (continuos normalization approximation, good to ~10 digits in this case)
P(x) = exp(-(x - mu)**2 / (2 * sigma**2)) / (sqrt(2 * pi) * sigma) * 100
# By sigma intervals:
oddsi(x) = (int(abs(x - mu) / sigma) % 2) ^ (x < mu)
Pm(x) =               (x == mu)  ? P(x) : 1/0 # sample at mu
Po(x) = ( oddsi(x) && (x != mu)) ? P(x) : 1/0 # samples in odd sigma intervals
Pe(x) = (!oddsi(x) && (x != mu)) ? P(x) : 1/0 # samples in even sigma intervals

set key off
set border 3
set xlabel 'IQ'
set xtics 10 out nomirror
set mxtics 2
set ylabel 'Population, %'
set ytics 1 out nomirror
set mytics 2
set samples (to - from + 1)
set style function impulses
plot [x = from:to] \
 Pm(x) lw 2, \
 Po(x) lw 2, \
 Pe(x) lw 2