R help - Nov 2008 - trouble with for loop

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.

?try 
> -----Original Message-----
> From: r-help-bounces at r-project.org 
> [mailto:r-help-bounces at r-project.org] On Behalf Of Kyeongmi Cheon
> Sent: Thursday, 6 November 2008 4:56 p.m.
> To: R help mailing list
> Subject: [R] trouble with for loop
> 
> 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.
> 
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