[R] plotting density for truncated distribution

[Jeroen Ooms]

I am using density() to plot a density curves. However, one of my variables
is truncated at zero, but has most of its density around zero. I would like
to know how to plot this with the density function.

The problem is that if I do this the regular way density(), values near zero
automatically get a very low value because there are no observed values
below zero. Furthermore there is some density below zero, although there are
no observed values below zero. 

This illustrated the problem: 

mydata <- rnorm(100000);
mydata <- mydata[mydata>0];
plot(density(mydata));

the 'real' density is exactly the right half of a normal distribution, so
truncated at zero. However using the default options, the line seems to
decrease with a nice curve at the left, with some density below zero. This
is pretty confusing for the reader. I have tried to decrease the bw, masks
(but does not fix) some of the problem, but than also the rest of the curve
loses smoothness. I would like to make a plot of this data that looks like
the right half of a normal distribution, while keeping the curve relatively
smooth.

Is there any way to specify this truncation in the density function, so that
it will only use the positive domain to calculate density?
-- 
View this message in context: http://www.nabble.com/plotting-density-for-truncated-distribution-tp20684995p20684995.html
Sent from the R help mailing list archive at Nabble.com.