[R] How to specify ff object filepaths when reading a CSV file into a ff data frame.

[Xiaobo Gu]

Hi,
    The read.csv.ffdf function in package ff will create the ff object
physical file in the default directories, I am trying to let the files
created in the paths users specify, I think the point is to make use
of the asffdf_args parameter,
I have a test CSV file named D:\rtemp\fftest.csv, the content of the
file is as following:

col1,col2,col3
1,"amber",2.4
2,"linda",4.5

I tried the following code, hoping ff will create the physical files
for col1,col2 and col3 to D:/a.f,D:/b.f,D:/c.f respectively

 fdf <- read.csv.ffdf(file="D:/rtemp/fftest.csv",asffdf_args = list(
col_args =  c(list(filename="D:/a.f"), list(filename="D:/b.f"),
list(filename="D:/c.f"))))
and the error message is :
Error in as.ff.default(1:2, vmode = NULL, filename = "D:/a.f",
filename = "D:/b.f",  :
  formal argument "filename" matched by multiple actual arguments

I also tried the following:

> fdf <- read.csv.ffdf(file="D:/rtemp/fftest.csv",asffdf_args = list( col_args =  list(filename=c("D:/a.f","D:/b.f","D:/c.f"))))
Error in ff(initdata = initdata, length = length, levels = levels,
ordered = ordered,  :
  bad argument initdata for existing file; initializing existing file is invalid
In addition: Warning messages:
1: In if (file.exists(filename)) { :
  the condition has length > 1 and only the first element will be used
2: In if (file.exists(filename)) { :
  the condition has length > 1 and only the first element will be used
3: In if (file.access(filename, 4) == -1) { :
  the condition has length > 1 and only the first element will be used
4: In if (file.access(filename, 2) == -1) { :
  the condition has length > 1 and only the first element will be used
5: In if (is.na(filesize)) stop("unable to open file") :
  the condition has length > 1 and only the first element will be used

My questions are:
1. What's the datatype of the col_args parameter of the as.ffdf function
2. If I can make layout of the asffdf_args parameter correct, how can
I set the exact filenames for each column of the ff data frame.

Regards,

Xiaobo Gu