file "Sorsby 1961-girls.dat":

 # Refractive error for girls of age 3...15
 # as a function of age and gender (mean ± SD)
 # 
 # SORSBY A, BENJAMIN B, SHERIDAN M, STONE J, LEARY GA:
 # Refraction and its components during the growth of the eye from the age of three.
 # Memo Med Res Counc. 1961;301(Special):1-67. PMID 13915328.
 #  Table 5.
 #
 # NOTE: values are mean RE, standard error SE of mean RE, and n: SD = SE * sqrt(n)
 #
 # age   RE (D)  SE (D)  n
 3       +2.96   0.19    39
 4       +2.33   0.15    51
 5       +2.20   0.17    58
 6       +1.83   0.19    54
 7       +1.98   0.20    57
 8       +1.63   0.15    60
 9       +2.03   0.24    56
 10      +1.33   0.20    63
 11      +1.50   0.20    85
 12      +1.04   0.19    60
 13      +0.96   0.13    61
 14      +0.62   0.26    80
 15      +0.64   0.181   37


file "Sorsby 1961-boys.dat":

 # Refractive error for boys of age 3...14
 # as a function of age and gender (mean ± SD)
 # 
 # SORSBY A, BENJAMIN B, SHERIDAN M, STONE J, LEARY GA:
 # Refraction and its components during the growth of the eye from the age of three.
 # Memo Med Res Counc. 1961;301(Special):1-67. PMID 13915328.
 #  Table 5.
 #
 # NOTE: values are mean RE, standard error SE of mean RE, and n: SD = SE * sqrt(n)
 #
 # age   RE (D)  SE (D)  n
 3       +2.33   0.24    56
 4       +2.24   0.12    54
 5       +2.21   0.16    56
 6       +1.71   0.16    56
 7       +1.92   0.20    64
 8       +1.76   0.19    60
 9       +1.52   0.24    50
 10      +1.43   0.22    51
 11      +1.63   0.23    57
 12      +1.19   0.23    67
 13      +1.38   0.20    58
 14      +0.93   0.38    42


file "CLEERE-girls.dat":
 # Refractive error for girls of age 6...14
 # (1997 to 1998 academic year) in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study,
 # as a function of age and gender (mean ± SD))
 #
 #  Zadnik et al: Ocular component data in schoolchildren as a function of age and gender.
 #  Optom Vis Sci. 2003 Mar;80(3):226-36. PMID 12637834.
 #   Table 3.
 #
 # age   RE (D)  SD (D)
 6       +0.88   0.86
 7       +0.78   1.01
 8       +0.64   1.26
 9       +0.18   1.64
 10      -0.004  1.42
 11      +0.03   1.72
 12      -0.16   1.55
 13      -0.15   1.38
 14      -0.46   2.18

file "CLEERE-boys.dat":
 # Refractive error for boys of age 6...14
 # (1997 to 1998 academic year) in the Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error (CLEERE) Study,
 # as a function of age and gender (mean ± SD)
 # 
 #  Zadnik et al: Ocular component data in schoolchildren as a function of age and gender.
 #  Optom Vis Sci. 2003 Mar;80(3):226-36. PMID 12637834.
 #   Table 3.
 #
 # age   RE (D)  SD (D)
 6       +0.81   0.87
 7       +0.72   0.95
 8       +0.52   1.11
 9       +0.37   1.14
 10      +0.34   1.25
 11      +0.18   1.57
 12      +0.32   1.50
 13      -0.12   1.58
 14      -0.11   2.78

file "Refractive_Error_Distribution.gnuplot.txt": 
 reset
 
 set terminal svg size 800 800 fixed  fname 'Times'  fsize 8 rounded dynamic
 set output "Refractive_Error_Distribution.svg"
 
 set style function lines
 
 set multiplot layout 2, 2 title "Normal Distribution of Refractive Error of Children aged 3 ... 15\n 1961 Data from [Sorsby et al. 1961], 1997 Data from CLEERE Study [Zadnik et al. 2003]"
 
 set grid
 set xtics 1
 set ytics 1
 set y2tics 1
 set xrange [3:15]
 set yrange [-5:+5]
 set y2range [-5:+5]
 
 set key left bottom
 
 set format y "%+g"
 set format y2 ""
 set xlabel "Girls (UK 1961) / Age"
 set ylabel "Refractive Error RE [dpt]"
 
 #
 # The Sorsby dataset provides standard error, not standard deviation. For conversion we need to multiply by sqrt(n)
 #
 plot "Sorsby 1961-girls.dat" \
            u 1:($2-2.58*$3*sqrt($4)):($2+2.58*$3*sqrt($4)) with filledcurve title "RE ± 2.58σ (99% CI)" lc rgb "#F5E3D0", \
         "" u 1:($2-2*$3*sqrt($4)):($2+2*$3*sqrt($4)) with filledcurve title "RE ± 2σ (95.45% CI)" lc rgb "#FAB068", \
         "" u 1:($2-$3*sqrt($4)):($2+$3*sqrt($4)) with filledcurve title "RE ± 1σ (68.27% CI)" lc rgb "#F04C2B", \
         "" u 1:2 with lines notitle lc rgb "#FAB068" lw 2
 
 set xlabel "Boys (UK 1961) / Age"
 unset ylabel
 set format y ""
 set format y2 "%+g"
 
 plot "Sorsby 1961-boys.dat" \
            u 1:($2-2.58*$3*sqrt($4)):($2+2.58*$3*sqrt($4)) with filledcurve title "RE ± 2.58σ (99% CI)" lc rgb "#C5E1EF", \
         "" u 1:($2-2*$3*sqrt($4)):($2+2*$3*sqrt($4)) with filledcurve title "RE ± 2σ (95.45% CI)" lc rgb "#2B8CBE", \
         "" u 1:($2-$3*sqrt($4)):($2+$3*sqrt($4)) with filledcurve title "RE ± 1σ (68.27% CI)" lc rgb "#045A8D", \
         "" u 1:2 with lines notitle lc rgb "#2B8CBE" lw 2
 
 set format y "%+g"
 set format y2 ""
 set xlabel "Girls (US 1997) / Age"
 set ylabel "Refractive Error RE [dpt]"
 plot "CLEERE-girls.dat" \
            u 1:($2-2.58*$3):($2+2.58*$3) with filledcurve title "RE ± 2.58σ (99% CI)" lc rgb "#F5E3D0", \
         "" u 1:($2-2*$3):($2+2*$3) with filledcurve title "RE ± 2σ (95.45% CI)" lc rgb "#FAB068", \
         "" u 1:($2-$3):($2+$3) with filledcurve title "RE ± 1σ (68.27% CI)" lc rgb "#F04C2B", \
         "" u 1:2 with lines notitle lc rgb "#FAB068" lw 2
 
 set xlabel "Boys (US 1997) / Age"
 unset ylabel
 set format y ""
 set format y2 "%+g"
 
 plot "CLEERE-boys.dat" \
            u 1:($2-2.58*$3):($2+2.58*$3) with filledcurve title "RE ± 2.58σ (99% CI)" lc rgb "#C5E1EF", \
         "" u 1:($2-2*$3):($2+2*$3) with filledcurve title "RE ± 2σ (95.45% CI)" lc rgb "#2B8CBE", \
         "" u 1:($2-$3):($2+$3) with filledcurve title "RE ± 1σ (68.27% CI)" lc rgb "#045A8D", \
         "" u 1:2 with lines notitle lc rgb "#2B8CBE" lw 2

command to generate SVG: "gnuplot Refractive_Error_Distribution.gnuplot.txt"