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Why doesn't merge work in the following? It gives error `Error:

require(ff)
require(ffbase)


a <- ffbase:::as.ff_matrix.ffdf(as.ffdf(data.frame(matrix(rnorm(10),ncol=2))))
b <- ffbase:::as.ff_matrix.ffdf(as.ffdf(data.frame(matrix(rnorm(10),ncol=2))))

a <- as.ffdf(a)
b <- as.ffdf(b)

colnames(a) <- 1:2
colnames(b) <- 3:4

a$RN <- as.ff(1:5)
b$RN <- as.ff(1:5)

c <- merge(a,b,by="RN") #ERROR

However if I do no casting it works:

a <- as.ffdf(data.frame(matrix(rnorm(10),ncol=2)))
b <- as.ffdf(data.frame(matrix(rnorm(10),ncol=2)))

colnames(a) <- 1:2
colnames(b) <- 3:4

a$RN <- as.ff(1:5)
b$RN <- as.ff(1:5)


c <- merge(a,b,by="RN")
user2763361
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  • The main question is: why do you want `merge` here? You have asked a similar question here already. http://stackoverflow.com/questions/20602908/how-can-i-use-merge-to-cbind-two-dataframes – Dieter Menne Dec 16 '13 at 07:40
  • It's to do with virtual and physical attributes. Run physical(a) in both cases... – shadow Dec 16 '13 at 09:14

1 Answers1

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Interesting. merge.ffdf is part of ffbase so this should work but apparently when doing ffbase:::as.ff_matrix.ffdf, PhysicalIsMatrix is still TRUE. This might mess up the generic dispatching.

ffdf (all open) dim=c(5,3), dimorder=c(1,2) row.names=NULL
ffdf virtual mapping
   PhysicalName VirtualVmode PhysicalVmode  AsIs VirtualIsMatrix PhysicalIsMatrix PhysicalElementNo PhysicalFirstCol PhysicalLastCol PhysicalIsOpen
1             x       double        double FALSE           FALSE             TRUE                 1                1               1           TRUE
2             x       double        double FALSE           FALSE             TRUE                 1                2               2           TRUE
RN           RN      integer       integer FALSE           FALSE            FALSE                 2                1               1           TRUE

Can you report this at https://github.com/edwindj/ffbase/issues. I'll have a look to see if I can change the unexported ffbase:::as.ff_matrix.ffdf. Thanks.