On Wed, 20 Apr 2011, Ravi Varadhan wrote:
If you had told us what the error message was, my job would have been easier.
But, at least you provied the code, so it was not hard for me to see where the
problem was. There is a problem with the strategy used by `qmvnorm' to locate
the initial interval in which the quantile is supposed to lie. In particular,
the problem is with the approx_interval() function.
In your case, the interval computed by this function does not contain the root.
Hence, uniroot() fails. The solution is to provide the interval that contains
the roots. I am cc'ing Torsten so that he is aware of the problem.
thanks, Ravi, for the report -- indeed, `tail = "upper"' caused
`approx_interval()' to act insane. Fixed in 0.9-99 on R-forge and soon on
CRAN.
Best,
Torsten
The following works:
m <- 10
rho <- 0.1
k <- 2
alpha <- 0.05
cc_z <- rep(NA, length=m)
var <- matrix(c(1,rho,rho,1), nrow=2, ncol=2, byrow=T)
for (i in 1:m){
if (i <= k) {cc_z[i] <- qmvnorm((k*(k-1))/(m*(m-1))*alpha, tail="upper",
sigma=var, interval=c(0, 5))$quantile} else
{cc_z[i] <- qmvnorm((k*(k-1))/((m-i+k)*(m-i+k-1))*alpha, tail
="upper", sigma=var, interval=c(0,5))$quantile}
}
cc_z
cc_z
[1] 1.9438197 1.9438197 1.8910860 1.8303681 1.7590806 1.6730814 1.5652220
[8] 1.4219558 1.2116459 0.8267921
Ravi.
________________________________________
From: r-help-boun...@r-project.org [r-help-boun...@r-project.org] On Behalf Of
li li [hannah....@gmail.com]
Sent: Wednesday, April 20, 2011 5:59 PM
To: r-help
Subject: [R] question regarding qmvnorm
Dear all,
I wrote the following function previously. It worked fine with the old
mvtnorm package.
Somehow with the updated package, I got a error message when trying to use
the function.
I need some help. It is sort of urgent. Can anyone please take a look. The
function is the following.
Thank you very much!
Hannah
library(mvtnorm)
cc_f <- function(m, rho, k, alpha) {
m <- 10
rho <- 0.1
k <- 2
alpha <- 0.05
cc_z <- numeric(m)
var <- matrix(c(1,rho,rho,1), nrow=2, ncol=2, byrow=T)
for (i in 1:m){
if (i <= k) {cc_z[i] <- qmvnorm((k*(k-1))/(m*(m-1))*alpha, tail="upper",
sigma=var)$quantile} else
{cc_z[i] <- qmvnorm((k*(k-1))/((m-i+k)*(m-i+k-1))*alpha, tail
="upper", sigma=var)$quantile}
}
cc <- 1-pnorm(cc_z)
return(cc)
}
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and provide commented, minimal, self-contained, reproducible code.
