[R] integrate dmvtnorm

[Ravi Varadhan]

The main problem is that your function is not vectorized.  Here is one
solution:

> require(mvtnorm)

> f=function(x){ sapply(x, function(y) {dmvnorm(c(0.6, 0.8), mean=c(0.75,
0.75/y))*dnorm(y, mean=0.6, sd=0.15)}) } 

> integrate(f, lower=-Inf, upper=Inf)
0.1314427 with absolute error < 4e-05
>

Hope this helps,
Ravi.


-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Carrie Li
Sent: Wednesday, June 23, 2010 7:06 PM
To: r-help
Subject: [R] integrate dmvtnorm

Hello, everyone,

I have a question about integration of product of two densities.
Here is the sample code; however the mean of first density is a function of
another random variable, which is to be integrated.

##
f=function(x) {dmvnorm(c(0.6, 0.8), mean=c(0.75, 0.75/x))*dnorm(x, mean=0.6,
sd=0.15)}
integrate(f, lower=-Inf, upper=Inf)

## error message
Error in dmvnorm(c(0.6, 0.8), mean = c(0.75, 0.75/x)) :
  mean and sigma have non-conforming size

I think it's because the mean in dmvnorm is a function of x....

is there any package or function to handle this question ?

Thanks for any help!

Carrie

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