I have an elementary programming question. Could someone please point
me in the right direction?
I have a function which will run for thousands of companies. At each
invocation, it returns 2 numbers. I plan to do something like:
think_one_firm <- function(filename) {
# Do stuff
return(list(x=x,y=y))
}
So for each of the firms in my dataset, I will call
think_one_firm(datafilename) and it will give me back two numbers x
and y. I could say:
l = think_one_firm("blah")
print(l$x); print(l$y);
and all would be fine.
What I want to do is: To tuck away the returned lists into a vector or
a data frame.
At the end, I would like to endup with a data structure allfirms
containing one 'row' for each firm. I guess this could be a data
frame, or a matrix, or a vector of lists (if such a thing exists). In
case it's a data frame, I would say allfirms$x[400] to access the
'x'
value returned for the 400th firm.
How would I do this?
--
Ajay Shah Consultant
ajayshah at mayin.org Department of Economic Affairs
http://www.mayin.org/ajayshah Ministry of Finance, New Delhi
Try this :
silly.fn <- function(x){ return( c(x^2, x^3) ) }
output <- matrix( nr=100, nc=2 )
for(i in 1:100){
my.x <- rnorm(1)
output[i, ] <- silly.fn( my.x )
rownames(output)[i] <- paste("Dataset", i, sep="")
}
colnames(output) <- c("squared", "cubed")
Notice that silly.fn returns a vector which is set to be the ith row of
output.
It is also possible to speed this with the apply family but this depends
on your input format. For example if your input was a list where the
first element corresponds to 1st company information in dataframe format
sapply( my.list.of.matrices, function(single.mat) some.fn(single.mat) )
Another option is to use output[i, ] <-
unlist(think_one_firm("blah"))
where unlist hopefully will convert the list to vector.
On Thu, 2004-06-17 at 18:26, Ajay Shah wrote:> I have an elementary programming question. Could someone please point
> me in the right direction?
>
> I have a function which will run for thousands of companies. At each
> invocation, it returns 2 numbers. I plan to do something like:
>
> think_one_firm <- function(filename) {
> # Do stuff
> return(list(x=x,y=y))
> }
>
> So for each of the firms in my dataset, I will call
> think_one_firm(datafilename) and it will give me back two numbers x
> and y. I could say:
>
> l = think_one_firm("blah")
> print(l$x); print(l$y);
>
> and all would be fine.
>
> What I want to do is: To tuck away the returned lists into a vector or
> a data frame.
>
> At the end, I would like to endup with a data structure allfirms
> containing one 'row' for each firm. I guess this could be a data
> frame, or a matrix, or a vector of lists (if such a thing exists). In
> case it's a data frame, I would say allfirms$x[400] to access the
'x'
> value returned for the 400th firm.
>
> How would I do this?
On Thu, 17 Jun 2004 22:56:29 +0530 Ajay Shah wrote:> I have an elementary programming question. Could someone please point > me in the right direction? > > I have a function which will run for thousands of companies. At each > invocation, it returns 2 numbers. I plan to do something like: > > think_one_firm <- function(filename) { > # Do stuff > return(list(x=x,y=y)) > } > > So for each of the firms in my dataset, I will call > think_one_firm(datafilename) and it will give me back two numbers x > and y. I could say: > > l = think_one_firm("blah") > print(l$x); print(l$y); > > and all would be fine. > > What I want to do is: To tuck away the returned lists into a vector or > a data frame. > > At the end, I would like to endup with a data structure allfirms > containing one 'row' for each firm. I guess this could be a data > frame, or a matrix, or a vector of lists (if such a thing exists). In > case it's a data frame, I would say allfirms$x[400] to access the 'x' > value returned for the 400th firm. > > How would I do this?If I understand correctly what you are trying to do, you could do the following: Suppose you have some firms: firms <- c("blah", "foo", "bar") and a function which computes something based on these firms thinkOneFirm <- function(firm) list(x = rnorm(1), y = rnorm(1)) (which for this example just returns random numbers, but let's imagine it's something more sensible :)) And then rval1 <- sapply(firms, thinkOneFirm) gives you a matrix with the numeric results. To get the desired data.frame you need to transpose and coerce rval2 <- as.data.frame(t(rval1)) and then you can get value x for firm "foo" by rval2$x["foo"] or rval2["foo", "x"] hth, Z> -- > Ajay Shah Consultant > ajayshah at mayin.org Department of Economic Affairs > http://www.mayin.org/ajayshah Ministry of Finance, New Delhi > > ______________________________________________ > R-help at stat.math.ethz.ch mailing list > https://www.stat.math.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html >