[R] ff objects saving problem

[Jens Oehlschlägel]

Xiaobo,

You indeed need external 'zip' and 'unzip' utlities in the path, citing from ffsave's help: "using an external zip utility, e.g. for windows in Rtools on [http://www.murdoch-sutherland.com/Rtools/]".

Please note that the mentioned utilities have a 4 GB limit for the zip file, AFAIK. I will for the next release check for a way to get rid of this limit and also to get rid of inconsistencies in upper/lower-case spelling of drive letters which can cause ffsave to fail. Note that - even without fffsave - ff objects can be made permanent simply by creating them with 'filename' resp. 'pattern' outside of fftempdir and saving the R-side ff-object with the usual 'save' or 'save.image' function. 

In a new R session, after 'library(ff)' and 'load' you again have access, assumed your ff files are still in the same location.
And yes, each column of a ffdf dataframe is stored as a separate ff file. 

Jens Oehlschlägel