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Re: st: calculate maximum density of normal distribuion


From   Nick Bornschein <[email protected]>
To   [email protected]
Subject   Re: st: calculate maximum density of normal distribuion
Date   Fri, 22 Nov 2013 16:36:22 +0100

I want to end the xline at the peak of the distribution curve, xline without any maximum just draws a line higher than the distributions maximum.



Am 22.11.13 16:34, schrieb Nick Cox:
If you know the mean, that fixes the position of the maximum; why do
you need any other information?
Nick
[email protected]


On 22 November 2013 15:32, Nick Bornschein <[email protected]> wrote:
Thanks, that worked!!

And now is the question: can I tell the xline (which is the mean) to end at
the maximum point somehow?



Am 22.11.13 16:29, schrieb Maarten Buis:

The mean won't do anything for the maximum, but the maximum is a
function of the standard deviation. It has to be otherwise the it
would not integrate to 1. So -normalden(0,$sd2)- will give you the
maximum.

-- Maarten


On Fri, Nov 22, 2013 at 4:23 PM, Nick Bornschein
<[email protected]> wrote:

Well, no.

The maximum density of a normal distribution of mean = 1 and sd = 2 is
around 0.2 (looking at the graph) and with mean = 5 and sd = 3 it's
around
1.125...so it's not always the same when I change the given mean and sd.


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
[email protected]


On 22 November 2013 15:00, Nick Bornschein <[email protected]>
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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