Dear all,
I know there have been various questions posted over the years about loops but
I'm afraid that I'm still stuck. I am using Windows XP and R 2.9.2.
I am generating some data using the multivariate normal distribution (within
the 'mnormt' package). [The numerical values of sanad and covmat are not
important.]
> datamat <-
> rmnorm(n=1500,mean=c(mean(sanad[,1]),mean(sanad[,2]),mean(sanad[,3])),varcov=covmat)
The middle column of 'datamat' is simulated data for age. Obviously some of
the simulated values are not going to be sensible. Therefore I'd like to set
up a function that looks at each row of 'datamat' and if the value for the
middle column is <5 or >86 then the whole row is replaced by another imputed
row. Of course, the problem is that the imputed value for age may be outside
my acceptable range too.
If there a way to set up a loop such that it keeps checking each row until the
values are within the range?
So far I have the following but this doesn't repeat the process.
ctstrunk <- function(data)
{
for(i in 1:nrow(data)){
if(data[i,2]<5)
data[i,]<-rmnorm(n=1,mean=c(mean(sanad[,1]),mean(sanad[,2]),mean(sanad[,3])),varcov=covmat)
if(data[i,2]>86)
data[i,]<-rmnorm(n=1,mean=c(mean(sanad[,1]),mean(sanad[,2]),mean(sanad[,3])),varcov=covmat)
}
return(data)
}
I thought of perhaps a repeat loop such as the following but this loop never
stops...
ctstrunk <- function(data)
{
repeat{
for(i in 1:nrow(data)){
if(data[i,2]<5)
data[i,]<-rmnorm(n=1,mean=c(mean(sanad[,1]),mean(sanad[,2]),mean(sanad[,3])),varcov=covmat)
if(data[i,2]>5){break}
}
repeat{
for(i in 1:nrow(data)){
if(data[i,2]>86)
data[i,]<-rmnorm(n=1,mean=c(mean(sanad[,1]),mean(sanad[,2]),mean(sanad[,3])),varcov=covmat)
if(data[i,2]<86){break}
}
return(data)
}
I have also tried a while loop but again, the function didn't stop
ctstrunk <- function(data)
{
for(i in 1:nrow(data)){
while(data[i,2]<5)
data[i,]<-rmnorm(n=1,mean=c(mean(sanad[,1]),mean(sanad[,2]),mean(sanad[,3])),varcov=covmat)
while(data[i,2]>86)
data[i,]<-rmnorm(n=1,mean=c(mean(sanad[,1]),mean(sanad[,2]),mean(sanad[,3])),varcov=covmat)
}
return(data)
}
Many thanks for any assistance you can offer.
Kind regards,
Laura
Laura Bonnett
Research Assistant
Department of Biostatistics
University of Liverpool
Telephone: 0151 7944059
Email: l.j.bonn...@liv.ac.uk
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