R: How to find the mean of a column in a data frame, that has non-numeric (specifically, dashes '-') as well as numeric numbers -

example of entries in data frame:

i need find mean of column in data frame, can't find mean says:

" argument not numeric or logical: returning na"

the non-numeric entries dash signs, have tried converting them na still struggling produce result mean.

can help?

try this, assuming data called dat:

dat[dat == "-"] <- na  mean(dat$population_and_people, na.rm = true]

ANy