Loading ff object after ff files were moved

Question

I had a CNSet object created by the crlmm package that was stored using ff package.

I saved it as an RData file (using the save function, not ffsave). And then I had to move my ff files to another location. Then I tried to load the object using the load function. But when I accessed a part of the object, I'm getting an error that the a ff file in the original location couldn't be found.

I set the new location using the ldPath function, but it's still looking in the old path.

Example:

library(ff)
ldPath('/new_location')
load('object.RData')
summary(g)
#Works, print:
#Length  Class   Mode
#1  CNSet     S4

calls(g)[1]
#Raises the next error:

opening ff /old/location/calld49920a2df79.ff

Error: file.access(filename, 0) == 0 is not TRUE

physical(x)

NULL

Any help will be appreciated.

Answer 1

You can specify the file path for ff object x with physical(x) <- 'my_file.ff'. For example:

library(ff)

old <- file.path(tempdir(), 'old.ff')         # this will be the original file path
new <- file.path(tempdir(), 'new.ff')         # this will be the new file path
x <- ff(1:4, filename=old)                    # create the original ff file
save(x, file = file.path(tempdir(), 'x.rda')) # save the ff object
close(x)                                      # close the ff object
file.rename(old, new)                         # rename the file
file.remove(old)                              # delete the old file
load(file.path(tempdir(), 'x.rda'))           # load the ff object
physical(x)$filename <- new                   # assign the new file path 

head(x)
## opening ff C:\Users\John\AppData\Local\Temp\Rtmp2ZEkgw/new.ff
## [1] 1 2 3 4