使 function 在 R 中的赋值运算符的 LHS 上工作

Question

It seems like I should know the answer to this but I don't. How can I write a function that will work on the lefthand side of the assignment operator? Eg, in the example below how can I make a function called my.rownames that I can put on the LHS of <- to assign rownames to foo .

# get rownames and change them
foo <- rownames(mtcars)
foo <- paste("x",foo)
# put altered rownames back
rownames(mtcars) <- foo
# create a new function my.rownames
my.rownames <- rownames
# works
my.rownames(mtcars)
# doesn't work
my.rownames(mtcars) <- foo

Answer 1

According to ?rownames

row.names returns a character vector.

row.names<- returns a data frame with the row names changed.

`my.rownames<-` <- `rownames<-`

Also,

There are generic functions for getting and setting row names, with default methods for arrays. The description here is for the data.frame method.

.rowNamesDF<- is a (non-generic replacement) function to set row names for data frames, with extra argument make.names. This function only exists as workaround as we cannot easily change the row.names<- generic without breaking legacy code in existing packages.

it should work

data(mtcars)
my.rownames(mtcars) <- foo
head(mtcars)
#                     mpg cyl disp  hp drat    wt  qsec vs am gear carb
#x Mazda RX4         21.0   6  160 110 3.90 2.620 16.46  0  1    4    4
#x Mazda RX4 Wag     21.0   6  160 110 3.90 2.875 17.02  0  1    4    4
#x Datsun 710        22.8   4  108  93 3.85 2.320 18.61  1  1    4    1
#x Hornet 4 Drive    21.4   6  258 110 3.08 3.215 19.44  1  0    3    1
#x Hornet Sportabout 18.7   8  360 175 3.15 3.440 17.02  0  0    3    2
#x Valiant           18.1   6  225 105 2.76 3.460 20.22  1  0    3    1