How to sum all values of a column of in a data.frame?

448    Asked by DominicPoole in Data Science , Asked on Jun 6, 2021

I have a data frame with several columns; some numeric and some character. How to compute the sum of a specific column? I’ve googled for this and I see numerous functions (sum, cumsum, rowsum, rowSums, colSums, aggregate, apply) but I can’t make sense of it all.

For example, suppose I have a data frame people with the following columns

Name Height Weight
Mary 65     110
John 70     200
Jane 64     115

How do I get the sum of all the weights?

Answered by Jack Russell

To solve how to sum a column in r you should put all values in a column of a data frame then use the sum() function from the base package as follows:

sum(people$Weight, na.rm = TRUE) 
#na.rm = TRUE will remove all 'NA' values in the column
For example:
df <- data.frame(p=c(10,8,7,3,2,6,7,8),
> df
   p v
1 10 100
2 8 300
3 7 150
4 3 400
5 2 450
6 6 250
7 7 150
8 8 400
sum(df$p, na.rm = TRUE)
[1] 51
Note - you can get built-in help by using ?sum, ?colSums, etc. (by the way, colSums will give you the sum for each column).

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