I can't name the columns of dataframe-CodePudding

m1 <- matrix(1:12, nrow=3, ncol=4)

m1$m1.sum <- rowSums(m1[, c(1,3)])

I just tried to use function ‘rowSums’ and R said that I have to name the columns.

    Warning message: 
In m1$m1.sum <- rowSums(m1[, c(1, 3)]) : Coercing LHS to a list

So I’ve tried to name the columns with the function ‘names’.

names(m1) <- c(1:4)

And I had problems like codes below. Idk What happened to my try. Would you give me a hand please?

     [,1] [,2] [,3] [,4]
[1,]    1    4    7   10
[2,]    2    5    8   11
[3,]    3    6    9   12
attr(,"names")
 [1] "1" "2" "3" "4" NA  NA  NA  NA  NA  NA  NA  NA

CodePudding user response：

The correct answer was provided by Rui Barradas, however, I suggest another solution that works with your code if m1 is a data.frame

Sample data:

m1<- data.frame(var1 = c(1, 2, 3),
                var2 = c(4, 5, 6),
                var3 = c(7, 8, 9),
                var4=c(10,11,12))

Sample code:

m1$row_sum <- rowSums(m1[ , c(1,3)], na.rm=TRUE)

Output:

  var1 var2 var3 var4 row_sum
1    1    4    7   10       8
2    2    5    8   11      10
3    3    6    9   12      12

CodePudding user response：

you could also use colnames() as follows:

m1 = data.frame(c(1, 2, 3),
                c(4, 5, 6),
                c(7, 8, 9),
                c(10,11,12))

colnames(m1) = c("var1", "var2", "var3", "var4")

and for renaming specific columns, for example the second, do:

colnames(m1)[2] = "var2_new"