Re: st: calculate maximum density of normal distribuion

[Nick Bornschein <nick.bornschein@gmail.com>]

Here is the code I'm using, change mean and sd at the beginning and look 
at the graph, the density is not the same:

clear
set obs 10000
set seed 2211
global mean = 5
global sd = 3
gen normal1 = rnormal($mean, $sd)

qui: su normal1
global min = r(min)
global min = round($min,.01)
display $min

qui: su normal1
global max = r(max)
global max = round($max,.01)
display $max

_pctile normal1, p(2.5)
global n1_1 = r(r1)
global n1_1 = round($n1_1,.01)
display $n1_1

_pctile normal1, p(97.5)
global n1_2 = r(r1)
global n1_2 = round($n1_2,.01)
display $n1_2

twoway  function y=normalden(x,$mean,$sd), range($min $max) color(r) || 
                            ///
function y=normalden(x,$mean,$sd), range($min $n1_1) recast(area) 
color(dknavy) ||          ///
        function y=normalden(x,$mean,$sd), range($n1_2 $max) 
recast(area) color(dknavy)             ///
        xtitle("{it: {&mu}}") 
                                     ///
        xline($mean) 
                                ///
        ytitle("") title("Normalverteilung") 
                                 ///
        subtitle("{&mu}=$mean {&sigma}=$sd mit {&alpha}=.05, 2-seitig") 
                              ///
        legend(off) xlabel($n1_1 $mean $n1_2)



Am 22.11.13 16:12, schrieb Nick Cox:
> That density is a constant, namely
>
> . di normalden(0)
> .39894228
>
> Whatever mean a normal has just shifts the distribution left or right,
> so makes no difference to what the peak density is; hence without loss
> of generality we can focus on mean 0.
>
> Whatever SD a normal has, 0/SD is still 0.
>
> Correct me if I'm wrong....
> Nick
> njcoxstata@gmail.com
>
>
> On 22 November 2013 15:00, Nick Bornschein <nick.bornschein@gmail.com> wrote:
> > Hello,
> >
> > I'm calculating a normal distribution with:
> >
> > set obs 10000
> > set seed 2211
> > gen normal2 = rnormal($mean2, $sd2)
> >
> > by given mean and sd which I define via global macro.
> >
> > Is it possible to calculate the maximum density at the mean point?
> > And more interesting: is it possible to define "xline" until a given point
> > at the y axis (the maximum density as you can imagine) because I want to add
> > the mean line with going higher than the maximum density?
> >
> > Best
> > -Nick
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