[R] trouble with for loop

[Kyeongmi Cheon]

Hello,
I'm having two similar problems with for loop and I would appreciate
any help or comment.

I want to use  "for loop" to calculate series of initial values for an
optimization problem. But

some initial values have my function quit due to problems like
calculating the inverse of singular

matrices. I don't want to make my program check determinants and skip it if it

is very small. My program stopping for certain iterations is okay but
my problem is that the whole

for loop is ended from there and it does not move to the next
iteration. So the rest of the initial values are

never tried. Here is a simple example:



mat.inv <- function(theta){
   mat1 <- matrix( theta, nr=2)
   inv <- solve(mat1)
   res <- theta[1]+inv[1,1]
   res
}

for (i in 1:7){
   theta4 <- i
   theta.vec <-  c(1,2,2,theta4)
   theta.res <- mat.inv(theta.vec)
   write.table(theta.res, paste("result",i,".txt",sep=""))
}

It stops when i=4. I need to try other values. How would I get it to
simply move on to the next

iteration :i=5,6,7 without checking determinants?



Another similar problem that I have is that I have thousands of txt
files and want to use a for loop

to read them into R. The file names are consecutive but some of them
are missing: For

example, they are "result1.txt", "result2.txt", "result3.txt",
"result5.txt"...  When I use for loop to read it, it gets an error at
"result4.txt" so that "result5.txt"...  are not read. I attached an
example program here. Could anyone help me? I appreciate your time in
advance.
Kyeongmi


#create dataset name
for (i in 1:6){
assign(paste("newname",i,sep=""), paste("result",i,".txt",sep=""))
}
ls()

#read data if there are files with the name: "result1.txt",
"result2.txt", "result3.txt",

"result5.txt".
for (i in 1:6){
      assign(  paste("r",i,sep=""),
read.table(get(paste("newname",i,sep="")), header=T)    )

}

# It stops at "result3.txt" so that "result5.txt"...  are not read.