[R] odd dnorm behaviour (?)

Mike Lawrence Mike.Lawrence at DAL.CA
Tue Jul 8 06:51:13 CEST 2008


#Let's try this again! This time the code is more sensible (curve  
range, same sd value).

#Quick one hopefully. Shouldn't dnorm be returning the pdf? Last time  
I checked,
#a probability shouldn't be greater than 1 as produced by:

curve(dnorm(x,0,.1),from=-.5,to=.5)

#Shouldn't I be getting an axis more like that produced by:

f=function(x,m,s){
	y=rep(NA,length(x))
	for(i in 1:length(x)){
		y[i]=integrate(
			dnorm
			, upper=x[i]+sqrt(.Machine$double.eps)
			, lower=x[i]-sqrt(.Machine$double.eps)
			, mean=m
			, sd=s
		)$value
	}
	return(y)
}
curve(f(x,0,.1),from=-.5,to=.5)

#If the latter code betrays a misunderstanding of what a pdf is, be  
gentle!

#Mike

--
Mike Lawrence
Graduate Student, Department of Psychology, Dalhousie University

www.memetic.ca

"The road to wisdom? Well, it's plain and simple to express:
Err and err and err again, but less and less and less."
	- Piet Hein



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