R中的data.frame

Question

I am a beginner in R, and I want to create an xlsx file from R. My data frame is defined as:

SP : List of 8
 $ WL          : num [1:1201] 200 200 201 202 202 ...
 $ t           : num [1:872, 1] 0.499 0.999 1.499 1.999 2.499 ...
 $ SP          : int [1:872, 1:1201, 1] 380 405 447 431 419 436 439 434 422 447 ...
 $ TF          : int [1:872, 1] 0 1 2 3 4 5 6 7 8 9 ...
 $ SpectraCount: num 872
 $ TStamp      : chr "12/01/2011 03:09:32PM"
 $ IT          : int 100
 $ SourceCount : num 1 

I want to transform the data.frame into a table with one column for each value of WL , and one row for each value of t , with the values inside the table as the SP for that combination of WL and t . The resulting table would look like:

               WL 1,.......... 1201
            t
            1         (SP values)
            .
            827

---

If i put

write.csv(SP1, file="SP1.csv", row.names = FALSE)

then i have Error in data.frame(WL = c(200, 200.5, 201, 201.5, 202, 202.5, 203, 203.5, : arguments imply differing number of rows: 1201, 872, 1

Answer 1

Maybe generating a csv file would be enough. Excel can read csv files. See write.csv for this.

Otherwise, there is write.xls from the dataframes2xls package, or write.xlsx from the xlsx package.

Answer 2

No Excel interface I know of can deal with ragged lists - you will need to convert that to a rectangular data structure.

You could of course loop over the columns of your list and write those, but I think you'd be better off just padding your list into a data.frame:

> l <- list(a="foo", b=c(1,2,3), d=(1.0,2.0,3.0,4.0))
> rows <- max(unlist(lapply(l, length)))
> padded <- lapply(l, function(col) c(col, rep(NA, rows-length(col))))
> as.data.frame(padded)
     a  b d
1  foo  1 1
2 <NA>  2 2
3 <NA>  3 3
4 <NA> NA 4

Then, you can use any of the Excel packages, with my favourite XLConnect :

> library(XLConnect)
> writeWorksheetToFile(file="out.xlsx", data=as.data.frame(padded), sheet="Output")