[R] invalid factor level, NAs generated

[Peter Ehlers]

On 2010-07-16 13:38, Jared Stabach wrote:
> I've seen a few threads about this, but none that seem to answer my problem
>
> I have a list of .txt files in a directory that I am reading into R and row
> binding together.  I am using the following code to do so:
>
> # Directory where files are found
> my.txt.file.directory<- "C:/Jared/Data/Kenya/Wildebeest/Tracking_Data"
>
> names.of.txt.files<-
> list.files(my.txt.file.directory,pattern="all_data",ignore.case=TRUE,
> full.names=TRUE)
> # Print names that meet criteria in directory
> names.of.txt.files
>
> # The names.of.txt.files will be a vector with the names of all the txt
> files
> # Dataset will contain all the data in the directory
>
> wildebeest<- NULL
> # Run loop
> for (i in 1:length(names.of.txt.files))
> {
> dat<- read.table(names.of.txt.files[i],header=FALSE)
> # Row bind all data together into a file called 'wildebeest'
> wildebeest<- rbind.data.frame(wildebeest,dat)
> rm(dat)
> }
>
> When I run this script, I get an error such as:
>
> 18: In `[<-.factor`(`*tmp*`, ri, value = c(1714.36, 1711.27,  ... :
>    invalid factor level, NAs generated
>
>
> I think I have identified the problem such that when I identify the
> structure of some of the files that I am reading in, columns are labeled as
> "Factors".  In other files, the same columns are labeled as numeric
> values.  Is there a way to assign the data structure to these columns in the
> dataframe as they are being read in?  Any other suggestions to why I am
> getting this error is appreciated.
>
> Jared

Jared,

I'd guess that you have invalid data in some of your files.
Perhaps missing values coded as '*' or as 'N/A'. If so, set
the na.strings= argument.

   -Peter Ehlers