diff --git a/guide/guide-16.svg b/guide/guide-16.svg
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+++ b/guide/guide-16.svg
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gnuplot_plot_1
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diff --git a/guide/guide-17.svg b/guide/guide-17.svg
new file mode 100644
index 0000000..d1c576d
--- /dev/null
+++ b/guide/guide-17.svg
@@ -0,0 +1,1621 @@
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diff --git a/guide/guide.org b/guide/guide.org
index b971a8f..0d62267 100644
--- a/guide/guide.org
+++ b/guide/guide.org
@@ -435,19 +435,48 @@ samples in [-1,1]: it should be normal-ish. And let's draw the expected perfect
PDF on top (as an equation, evaluated by =gnuplot=).
#+BEGIN_SRC sh :results file link :exports both
-N=1000;
-Nsum=200;
-var=$((Nsum/3));
-binwidth=2;
+N=20000;
+Nsum=10;
+binwidth=.1;
seq $N | \
perl -nE '$Nsum = '$Nsum';
+ $var = '$Nsum' / 3.;
$s = 0; for $i (1..$Nsum) { $s += rand()*2-1; }
- say $s;' | \
+ say $s/sqrt($var);' | \
feedgnuplot --histo 0 --binwidth $binwidth \
- --equation-above "($N * sqrt(2.*pi*$var) * erf($binwidth/(2.*sqrt(2.*$var)))) * \
- exp(-(x*x)/(2.*$var)) / \
- sqrt(2.*pi*$var) title \"Limit gaussian\" with lines lw 2"
+ --equation-above "($N * sqrt(2.*pi) * erf($binwidth/(2.*sqrt(2.)))) * \
+ exp(-(x*x)/(2.)) / \
+ sqrt(2.*pi) title \"Limit gaussian\" with lines lw 2"
#+END_SRC
#+RESULTS:
[[file:guide-16.svg]]
+
+If we want multiple histograms drawn on top of one another, the styling should
+be adjusted so that they both remain visible. Let's vary the size of the sum,
+and look at the effects: bigger sums should be more gaussian-like:
+
+#+BEGIN_SRC sh :results file link :exports both
+N=20000;
+binwidth=.1;
+for Nsum in 1 2 3; do
+ seq $N | \
+ perl -nE '$, = " ";
+ $Nsum = '$Nsum';
+ $var = '$Nsum' / 3.;
+ $s = 0; for $i (1..$Nsum) { $s += rand()*2-1; }
+ say $Nsum,$s/sqrt($var);';
+done | \
+feedgnuplot --dataid --histo 1,2,3 --binwidth $binwidth \
+ --autolegend \
+ --style 1 'with boxes fill transparent solid 0.3 border lt -1' \
+ --style 2 'with boxes fill transparent pattern 4 border lt -1' \
+ --style 3 'with boxes fill transparent pattern 5 border lt -1' \
+ --equation-above "($N * sqrt(2.*pi) * erf($binwidth/(2.*sqrt(2.)))) * \
+ exp(-(x*x)/(2.)) / \
+ sqrt(2.*pi) title \"Limit gaussian\" with lines lw 2"
+#+END_SRC
+
+#+RESULTS:
+[[file:guide-17.svg]]
+