[R] Add Gauss normal curve ?

[varin sacha]

Dear Peter, 
Dear David,

Many thanks for your response. 
Indeed, counts do not have a Gaussian distribution, even if.... sometimes one approximates the distribution by a Gaussian one, usually using the argument of the Central Limit Theorem.

Here below the reproducible example. 
One last thing. Now if I want to move my red Gaussian curve to the right or to the left, for example on the graph I can see that the Gaussian curve is centered around the 5th of April.

Is it possible to move the Gaussian curve to make the center of the Gaussian curve on the 30th of March for example ? If yes, how to do ?

############################################################
mydates <- as.Date(c("2020-03-15", "2020-03-16","2020-03-17","2020-03-18","2020-03-19","2020-03-20","2020-03-21","2020-03-22","2020-03-23","2020-03-24","2020-03-25","2020-03-26","2020-03-27","2020-03-28","2020-03-29","2020-03-30","2020-03-31","2020-04-01","2020-04-02","2020-04-03","2020-04-04","2020-04-05","2020-04-06","2020-04-07","2020-04-08","2020-04-09","2020-04-10"))

nc<-c(1,1,2,7,3,6,6,20,17,46,67,71,56,70,85,93,301,339,325,226,608,546,1069,1264,1340,813,608)

plot(as.Date(mydates),nc,pch=16,type="o",col="blue",ylim=c(1,1400), xlim=c(min(as.Date(mydates)),max(as.Date(mydates))))

y <- rep(mydates, nc)
n <- sum(nc)
curve(n*dnorm(x, mean(y), sd(y)), add=TRUE, col="red", lwd=2)
############################################################







Le samedi 11 avril 2020 à 17:02:36 UTC+2, peter dalgaard <pdalgd using gmail.com> a écrit : 





Two obvious problems: 

1. mean(nc) is a count, not a date, sd likewise
2. the scale of dnorm() is density, not count

So (slightly inefficient, but who cares...):

y <- rep(mydates, nc)
n <- sum(nc)
curve(n*dnorm(x, mean(y), sd(y)), add=TRUE, col="red", lwd=2)

-pd

> On 11 Apr 2020, at 16:00 , varin sacha via R-help <r-help using r-project.org> wrote:
> 
> Dear R-experts,
> 
> Here below my reproducible example. I would like to fit/add the Gauss normal curve to this data. 
> I don't get it. There is no error message but I don't get what I am looking for. 
> Many thanks for your help.
> 
> ############################################################
> mydates <- as.Date(c("2020-03-15", "2020-03-16","2020-03-17","2020-03-18","2020-03-19","2020-03-20","2020-03-21","2020-03-22","2020-03-23","2020-03-24","2020-03-25","2020-03-26","2020-03-27","2020-03-28","2020-03-29","2020-03-30","2020-03-31","2020-04-01","2020-04-02","2020-04-03","2020-04-04","2020-04-05","2020-04-06","2020-04-07","2020-04-08","2020-04-09","2020-04-10"))
> 
> nc<-c(1,1,2,7,3,6,6,20,17,46,67,71,56,70,85,93,301,339,325,226,608,546,1069,1264,1340,813,608)
> 
> plot(as.Date(mydates),nc,pch=16,type="o",col="blue",ylim=c(1,1400), xlim=c(min(as.Date(mydates)),max(as.Date(mydates))))
> 
> x <- seq(min(mydates), max(mydates), 0.1) 
> 
> curve(dnorm(x, mean(nc), sd(nc)), add=TRUE, col="red", lwd=2)
> ############################################################
> 
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-- 
Peter Dalgaard, Professor,
Center for Statistics, Copenhagen Business School
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