[R] dnorm

[Greg Snow]

You need to take into account the bin width as well (hence the extra multiple you asked about), but it is simpler to just include prob=TRUE in the hist call, then you do not need to do any adjustment on the y-values of the reference distribution.

-- 
Gregory (Greg) L. Snow Ph.D.
Statistical Data Center
Intermountain Healthcare
greg.snow at imail.org
801.408.8111


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of "Sibylle Stöckli"
> Sent: Thursday, September 23, 2010 1:43 AM
> To: r-help at r-project.org
> Subject: [R] dnorm
> 
> Dear R-users
> 
> Idea:
> Plot a dnorm line using specific mean/sd to complete a histogram
> (skewed). xs:range of y-values, ys: dnorm function
> 
> Problem:
> I expected to multiply the ys function with the sample size (n=250-
> 300). I was wondering about a factor between 12'000 and 30'000 to match
> the size of the dnorm line with the specific histogram.
> 
> Thanks
> Sibylle
> 
> hist(Biotree[Ld,]$Height2008, main="Larix decidua", ylim=c(0,50),
> xlab="Tree Height 2008 (cm)",col="aquamarine", font.main=3,
> cex.axis=0.8)
> xs<-0:650
> ys<-dnorm(xs, mean=397.8, sd=97.6)
> lines(xs,ys*12000)
> 
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