Dplyr - Mean for multiple columns

Question

I want to calculate the mean for several columns and thus create a new column for the mean using dplyr and without melting + merging.

> head(growth2)   CODE_COUNTRY CODE_PLOT IV12_ha_yr IV23_ha_yr IV34_ha_yr IV14_ha_yr IV24_ha_yr IV13_ha_yr 1            1         6       4.10       6.97         NA         NA         NA       4.58 2            1        17       9.88       8.75         NA         NA         NA       8.25 3            1        30         NA         NA         NA         NA         NA         NA 4            1        37      15.43      15.07      11.89      10.00      12.09      14.33 5            1        41      20.21      15.01      14.72      11.31      13.27      17.09 6            1        46      12.64      14.36      13.65       9.07      12.47      12.36 >  

I need a new column within the dataset with the mean of all the IV columns. I tried this:

growth2 %>%    group_by(CODE_COUNTRY, CODE_PLOT) %>%   summarise(IVmean=mean(IV12_ha_yr:IV13_ha_yr, na.rm=TRUE)) 

And returned several errors depending on the example used, such as:

Error in NA_real_:NA_real_ : NA/NaN argument 

or

Error in if (trim > 0 && n) { : missing value where TRUE/FALSE needed 

Answer 1

You don't need to group, just select() and then mutate()

library(dplyr) mutate(df, IVMean = rowMeans(select(df, starts_with("IV")), na.rm = TRUE)) 

Answer 2

Use . in dplyr.

library(dplyr) mutate(df, IVMean = rowMeans(select(., starts_with("IV")), na.rm = TRUE))