mean() warning: argument is not numeric or logical: returning NA

From R 3.0.0 onwards mean(<data.frame>) is defunct (and passing a data.frame to mean will give the error you state)

A data frame is a list of variables of the same number of rows with unique row names, given class "data.frame".

In your case, result has two variables (if your description is correct) . You could obtain the column means by using any of the following

lapply(results, mean, na.rm = TRUE)
sapply(results, mean, na.rm = TRUE)
colMeans(results, na.rm = TRUE)

If you just want to know the mean, you can use

summary(results)

It will give you more information than expected.

ex) Mininum value, 1st Qu., Median, Mean, 3rd Qu. Maxinum value, number of NAs.

Furthermore, If you want to get mean values of each column, you can simply use the method below.

mean(results$columnName, na.rm = TRUE)

That will return mean value. (you have to change 'columnName' to your variable name