CODEWITHSUNDEEP
r
jay.sf
jay.sf

Reputation: 72919

How to set row names while creating an object?

Is there any option in base R, how to set the row and columns names, i. e. dimension names while creating an object in base R?

Example:

Assuming we have a data frame 'dfe'.

set.seed(8803)
dfe <- data.frame(V1=sample(1:10, 3),
                  V2=sample(1:10, 3),
                  V3=sample(1:10, 3), 
                  V4=sample(1:10, 3))
dfe
#   V1 V2 V3 V4
# 1  3  7  1  6
# 2  9  4  6  5
# 3  5  2  8  9

We can set column names with names(dfe) <- month.abb[1:4] or (for data frames) colnames(dfe) <- month.abb[1:4]. Accordingly for the row names rownames(dfe) <- LETTERS[1:3].

We also can do both in one process with dimnames(). Together with creating the data frame there are two steps though.

dfe <- data.frame(.)
dimnames(dfe) <- list(LETTERS[1:3], month.abb[1:4])
dfe
#   Jan Feb Mar Apr
# A   3   3   2   1
# B   9   4   6   9
# C  10   1   5   5

With setNames() we can give column names while creating the data frame.

dfe <- setNames(data.frame(V1=sample(1:10, 3),
                  V2=sample(1:10, 3),
                  V3=sample(1:10, 3), 
                  V4=sample(1:10, 3)), month.abb[1:4])
names(dfe)
# [1] "Jan" "Feb" "Mar" "Apr"

Have I missed something for the row names, even better dimension names in base R that sets these while creating an object? I couldn't find something like setRowNames() or setDimNames(). How do you do this?

Note: The solution should be rather be a general solution for objects than just fitting for creating data frames or matrices.

Upvotes: 1

Views: 816

Answers (1)

G. Grothendieck
G. Grothendieck

Reputation: 269654

This works for both data frames and matrices. Here BOD is a data frame that comes with R but this code also works if we replace BOD with as.matrix(BOD)

"rownames<-"(BOD, letters[1:6])

Upvotes: 3

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