?truehist in library(MASS)?
library(MASS)
truehist(samp)
x <- seq(-8.5, -6, length=51)
lines(x, dnorm(x, mean(samp), sqrt(var(samp))))
This just worked for me in both S-Plus 6.2 and R 1.8.1.
hope this helps. spencer graves
Rolf Turner wrote:
In response to a posting from WeiQiang Li:
Hi,
I am facing the problem that I want to plot a histogram chart set
freq to true and overlay with normal or weibull or exponential distribution
curve.
The sample code is shown as below:
samp<-c(-8.2262,-8.2262,-8.2262,-8.20209,-8.09294,-8.07321,-8.07321,
-8.07321,-8.07175,-8.04948,-8.04948,-8.04948,-8.03848,-8.03848,
-8.026,-7.92517,-7.92517,-7.77218,-7.62414,-7.62414,-7.62414,
-7.59027,-7.59027,-7.59027,-7.59027,-7.59027,-7.59027,-7.28924,
-7.28924,-6.78729,-6.25307)
hist(samp,freq=TRUE,br=20)
curve(dnorm(x,mean=mean(samp),sd=sd(samp)),add=TRUE)
In the chart created based on above command, curve scale is too small
compared to the freqeunce. My question here is how to adjust the scale of
distribution curve. Thanks !
Gabor Grothendieck wrote:
histdata <- hist(samp,freq=TRUE,br=20)
curve(max(histdata$count)*dnorm(x,mean=mean(samp),sd=sd(samp)),add=TRUE)
This is a perfectly correct answer to a question that should not have
been asked in the first place. What WeiQiang Li proposes to do makes
no sense at all, and will simply confuse and mislead the viewer/reader.
If a histogram is to be overlaid with a density curve that histogram
should represent a density and hence should be plotted on the density
scale --- NOT on the frequency scale.
cheers,
Rolf Turner
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