[R] a question on sqldf's handling of missing value and factor

From: xin wei <xinwei_at_stat.psu.edu>
Date: Tue, 01 Mar 2011 20:52:51 -0800 (PST)

Dear subscribers:

I am using the following code to read a large number of big text files: library(sqldf)
tempd <- file(XXXX)
tempdx <- sqldf("select * from tempd", dbname = tempfile(), file.format = list(header = T, sep="\t", row.names = F))

The problem is: all my numberical variable become factor (maybe because these columns all contain missing value). It would be quite cubersome to convert them to numeric variable using as.numeric one by one. Does anyone know how to re-set SQLDF so that it would automatically read the numeric column with missing row as real numeric instead of factor?

many thanks

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