Hi, My next problem is that I have a data frame with an years column. This column for some reason is recognised as factor instead of being numeric. The years go from 1970 to 2007. When I convert it to numeric with as.numeric then it goes from 1 to 38. Is there a way to convert it with saving its "levels"? This would be actually important as I am affraid of converting my real values that are recognised as factors as well. Thanks, Viktor
how to force years as.numeric?
2 messages · Viktor Nagy, Marc Schwartz
on 12/10/2008 06:54 PM Viktor Nagy wrote:
Hi, My next problem is that I have a data frame with an years column. This column for some reason is recognised as factor instead of being numeric. The years go from 1970 to 2007. When I convert it to numeric with as.numeric then it goes from 1 to 38. Is there a way to convert it with saving its "levels"? This would be actually important as I am affraid of converting my real values that are recognised as factors as well. Thanks, Viktor
Viktor, I would be concerned as to why a column that presumably only contains numeric values is being coerced to a factor to begin with. That would normally only occur when a column contains non-numeric characters. read.table(), for example, uses type.convert() internally to do that and the logic for the type coercion from a character vector is pretty straight-forward. Thus, you may have corrupted year values or at least corrupted characters in that particular column. I would recommend reviewing that data to get a sense of what is going on before proceeding. In general, FAQ 1.10 "How do I convert factors to numeric?" covers the process of converting factors containing numeric characters back to their numeric values: http://cran.r-project.org/doc/FAQ/R-FAQ.html#How-do-I-convert-factors-to-numeric_003f HTH, Marc Schwartz