sum two columns in R

Question

I feel a bit embarrassed as I am trying to add two columns in R to get the product.

I have tried

sum(col1,col2)

but this returns

Error in Summary.factor(c(49L, 48L, 47L, 46L, 46L, 45L, 45L, 44L, 43L,  : 
  sum not meaningful for factors

I thought this would very simple! both columns contain integers.

Answer 1

The sum function will add all numbers together to produce a single number, not a vector (well, at least not a vector of length greater than 1).

It looks as though at least one of your columns is a factor. You could convert them into numeric vectors by checking this

head(as.numeric(data$col1))  # make sure this gives you the right output

And if that looks right, do

data$col1 <- as.numeric(data$col1)
data$col2 <- as.numeric(data$col2)

You might have to convert them into characters first. In which case do

data$col1 <- as.numeric(as.character(data$col1))
data$col2 <- as.numeric(as.character(data$col2))

It's hard to tell which you should do without being able to see your data.

Once the columns are numeric, you just have to do

data$col3 <- data$col1 + data$col2