Hello,
I get an error using the [-operator for a data table object that is hard
to understand. Basically, what I want to do is the following: I have a
data.table with a number of binary patterns, possibly including IDs or
other additional columns. I want to process them grouped by the outcome
of some variables, e.g. count the number of examples that have 1s in
some specified columns. Unfortunately, I cannot reproduce the error with
simple test data, but with data from our package RecordLinkage:
install.packages("RecordLinkage") # just for convenienve as this is not
a common package
library(RecordLinkage)
library(data.table)
data(RLdata500)
rpairs <- compare.dedup(RLdata500, blockfld=list(5,6,7))
p <- rpairs$pairs
p[is.na(p)] <- 0
p <- data.table(p)
# Everything up to here sets up test data. Now define a key and
aggregate by the key columns
keyCol <- c("fname_c1", "lname_c2")
key(p) <- keyCol
p[, length(fname_c2), by=keyCol]
The last expression results in:
Fehler in `[[<-.data.frame`(`*tmp*`, jj, value = 0:1) :
replacement has 2 rows, data has 15627
However, when I construct a similar table manually, everything works fine:
expr <- quote(as.numeric(sample(0:1, 1000, replace=TRUE)))
dt <- data.table(fname_c1=eval(expr), fname_c2=eval(expr))
key(dt) <- c("fname_c1", "fname_c2")
dt[, length(fname_c2), by=c("fname_c1", "fname_c2")]
Also, with other combinations of attributes I get the first example
working as well:
keyCol <- c("fname_c1", "lname_c2")
key(p) <- keyCol
p[, length(fname_c2), by=keyCol]
I am not even sure if the error is strictly reproducible.
Any idea what could be wrong?
Best regards,
Andreas
--
Andreas Borg
Medizinische Informatik
UNIVERSITÄTSMEDIZIN
der Johannes Gutenberg-Universität
Institut für Medizinische Biometrie, Epidemiologie und Informatik
Obere Zahlbacher Straße 69, 55131 Mainz
www.imbei.uni-mainz.de
Telefon +49 (0) 6131 175062
E-Mail: [email protected]
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