Load Excel file to R while setting column equal to a factor

Question

I have an Excel file that I am trying to load into R using the odbcConnectExcel and sqlQuery commands from RODBC package. One of the columns has numerical values with plus or minus signs, such as '5+ or '3-. However, if i do something like,

conn <- odbcConnectExcel("file.xls")
sqlQuery(conn, "SELECT * FROM `Sheet1$`")

then the column with the plus and minus signs will be returned as a numerical column with those symbols stripped. Is there a way to have this column read in as a factor in which the signs are maintained? I would prefer to not have to convert the file to another format first.

Thanks.

Answer 1

Data like this becomes a factor if you use the xlsReadWrite (http://www.swissr.org/software/xlsreadwrite) package to read the file:

library(xlsReadWrite)
x <- read.xls(file="file.xls")

However, note that you need to do something more than just install.packages("xlsReadWrite") to get this package to run. You need another file or so, I forgot.

Answer 2

This doesn't directly address your question, but hopefully it will help:

This is the best summary of options for connecting to Excel that I have seen: Export Data Frames To Multi-worksheet Excel File. While it deals generally with exporting, importing is also possible with most of these approaches.

My favorite is actually the RDCOMClient because it provides total control over Excel as an application.