[R] How to subset an 'ff' object?

[Christofer Bogaso]

Hi Arun,

I will look into why dput is giving error......... In the mean time I am
attaching the csv file with this mail, however not sure if R-hep will
accept it.

I tried to converting it data.frame. However as 'Dat' is of huge size (that
is why I loaded it via ff route), converting the entire data to data.frame
giving memory allocation problem.

Thanks and regards,


On Sun, Dec 29, 2013 at 12:03 AM, arun <smartpink111 at yahoo.com> wrote:

> HI,
>
> The dput() is showing error message.
> Is it not possible to convert it to data.frame and subset?
>
> Using the example from ?ffdf
>  m <- matrix(1:12, 3, 4, dimnames=list(c("r1","r2","r3"),
> c("m1","m2","m3","m4")))
>        v <- 1:3
>        ffm <- as.ff(m)
>        ffv <- as.ff(v)
>   ffd <- ffdf(ffm, v=ffv, row.names=row.names(ffm))
> d1 <- data.frame(ffd)
>
>
> subset(d1,m1>1)
>    m1 m2 m3 m4 v
> r2  2  5  8 11 2
> r3  3  6  9 12 3
>
>
> A.K.
>
>
> On Saturday, December 28, 2013 12:29 PM, Christofer Bogaso <
> bogaso.christofer at gmail.com> wrote:
> Hi again,
>
> I have loaded a huge csv file in R using 'ff' package, however could not
> understand how can I subset the loaded object. Below is my try:
>
> > suppressMessages(library(ff))
> >
> > Dat <- read.csv.ffdf(file = "f:/Book1.csv", header = F, colClasses =
> c('Date', 'factor'))
> > Dat
> ffdf (all open) dim=c(4,2), dimorder=c(1,2) row.names=NULL
> ffdf virtual mapping
>    PhysicalName VirtualVmode PhysicalVmode  AsIs VirtualIsMatrix
> PhysicalIsMatrix PhysicalElementNo PhysicalFirstCol PhysicalLastCol
> PhysicalIsOpen
> V1           V1       double        double FALSE           FALSE
> FALSE                 1                1               1           TRUE
> V2           V2      integer       integer FALSE           FALSE
> FALSE                 2                1               1           TRUE
> ffdf data
>           V1         V2
> 1 2013-12-28 a
> 2 2013-12-28 b
> 3 2013-12-27 c
> 4 2013-12-27 c
> >
> > subset(Dat, Dat$V1 == as.Date('2013-12-27'))
> ffdf (all open) dim=c(4,0), dimorder=c(1,2) row.names=NULL
> ffdf virtual mapping
> [1] PhysicalName      VirtualVmode      PhysicalVmode     AsIs
> VirtualIsMatrix   PhysicalIsMatrix  PhysicalElementNo PhysicalFirstCol
> PhysicalLastCol
> [10] PhysicalIsOpen
> <0 rows> (or 0-length row.names)
> ffdf data
> [1] "[empty matrix]"
>
>
>
> My resulting object is showing '0' rows!
>
>
> The 'Dat' object looks like below:
>
> > dput(Dat)
> structure(list(virtual = structure(list(VirtualVmode = c("double",
> "integer"), AsIs = c(FALSE, FALSE), VirtualIsMatrix = c(FALSE,
> FALSE), PhysicalIsMatrix = c(FALSE, FALSE), PhysicalElementNo = 1:2,
>     PhysicalFirstCol = c(1L, 1L), PhysicalLastCol = c(1L, 1L)), .Names =
> c("VirtualVmode",
> "AsIs", "VirtualIsMatrix", "PhysicalIsMatrix", "PhysicalElementNo",
> "PhysicalFirstCol", "PhysicalLastCol"), row.names = c("V1", "V2"
> ), class = "data.frame", Dim = c(4L, 2L), Dimorder = 1:2), physical =
> structure(list(
>     V1 = structure(list(), physical = <pointer: 0x0298f498>, virtual =
> structure(list(), Length = 4L, Symmetric = FALSE, ramclass = "Date"), class
> = c("ff_vector",
>     "ff")), V2 = structure(list(), physical = <pointer: 0x0298f4c8>,
> virtual = structure(list(), Length = 4L, Symmetric = FALSE, Levels = c("a",
>     "b", "c"), ramclass = "factor"), class = c("ff_vector", "ff"
>     ))), .Names = c("V1", "V2")), row.names = NULL), .Names = c("virtual",
> "physical", "row.names"), class = "ffdf")
>
>
> Can experts here guide me how to subset that?
>
> Thanks for your time.
>
>     [[alternative HTML version deleted]]
>
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