[R] invalid factor level, NAs generated

[Erik Iverson]

<snip>

> 
> 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.
> 

Yes, as ?read.table describes, see the colClasses argument.

However, you should investigate why read.table wants to treat these 
particular columns as factors.  If they are indeed simply consisting of 
all numeric values, there shouldn't be a problem.  The fact that they 
are coming out as factors raises a flag to me ...