Doran, Harold wrote:
Dear List:
I am generating N datasets using the following
Sigma<-matrix(c(400,80,80,80,80,400,80,80,80,80,400,80,80,80,80,400),4,4 ) mu<-c(100,150,200,250)
N=100
for(i in 1:N) { assign(paste("Data.", i, sep=''),
as.data.frame(cbind(seq(1:1000),(mvrnorm(n=1000, mu, Sigma)))))
}
With these datasets, I need to work on some of the variables and then
run each dataset through a linear model. I am having some trouble
working with variables within the loop and wonder if anyone can offer
any pointers.
The first thing I am trying to do is add 2 variables together that are in each dataset. I am sure this is extremely trivial, but I can't seem to get that to work.
I have tried:
for (i in 1:5){ assign(paste("x",i,sep=""),(get(paste("Data.",i,sep=""))[["V2"]])+(get(p aste("Data.",i,sep=""))[["V2"]])) }
It's time to forget those 100 separate R objects, but try to work with a list, which makes life worth living again. ;-)
I'm reusing most of your code:
Sigma <- matrix(
c(400,80,80,80,80,400,80,80,80,80,400,80,80,80,80,400),
4, 4)
mu <- c(100,150,200,250)
N <- 100 Data <- lapply(seq(N), function(x)
as.data.frame(cbind(1:1000, mvrnorm(n=1000, mu, Sigma))))# so we have a list Data with 100 elements, # each containing a data.frame.
for(i in seq(along=Data))
Data[[i]]$V6 <- Data[[i]]$V1 + Data[[i]]$V2
Uwe Ligges
Now, this code works, but I want for this vector to be a variable within each dataframe. Outside the loop, the equivalent code would be
attach(Data.1) Data.1$V6<-V1+V2 Detach(Data.1)
Another task I would like to perform is to reshape each dataframe for longitudinal analysis. I have tried the following:
for (i in 1:5){
assign(paste("long",i,sep=""),reshape(paste("Data.",i,sep=""),idvar=get(
paste("Data.",i,sep="")[["V1"]]),
varying=list(names(get(paste("Data",i,sep="")[["V2"]]):get(paste("Data",
i,sep="")[["V5"]])),v.names="score",direction="long")
}
This isn't working and I'm not sure if the code is even close.
In general, performing all of these operations outside a loop for a
single dataframe is simple. My trouble is performing equivalent
operations within a loop.
Thanks for any help offered.
Harold
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