as.numeric() converts values to numbers, but I suspect you have some non-numeric values somewhere in those columns that you'll have to clean out first. Unless all the values are numeric, import will fall back to character or factor
Also, please note that we are not able to do general R-help here, and try to limit our support to questions about the ROpenSci packkage, as well as more discussions about scientific computing and reproducibility. For
support on R questions in general, I would recommend:
By all means, please continue to use this forum if you have questions about our packages! It's helpful to know how people use them and what we can make better.