Sum all values in every column of a data.frame in R

mapply(sum,people[,-1])

Height Weight 
   199    425 

You can use function colSums() to calculate sum of all values. [,-1] ensures that first column with names of people is excluded.

 colSums(people[,-1])
Height Weight 
   199    425

Assuming there could be multiple columns that are not numeric, or that your column order is not fixed, a more general approach would be:

colSums(Filter(is.numeric, people))

We can use dplyr to select only numeric columns and purr to get sum for all columns. (can be used to get what ever value for all columns, such as mean, min, max, etc. )

library("dplyr")
library("purrr")

people %>%
    select_if(is.numeric) %>%
    map_dbl(sum)

Or another easy way by only using dplyr - As of (dplyr 1.0.0) we can use across()

library("dplyr")
people %>%
    summarise(across(where(is.numeric), ~ sum(.x, na.rm = TRUE)))

---

library("dplyr")
people %>%
    summarize_if(is.numeric, sum, na.rm=TRUE)