rename the columns name after cbind the data

Question

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merger <- cbind(as.character(Date),weather1$High,weather1$Low,weather1$Avg..High,weather1$Avg.Low,sale$Scanned.Movement[a])

After cbind the data, the new DF has column names automatically V1, V2...... I want rename the column by

colnames(merger)[,1] <- "Date"

but failed. And when I use merger$V1 ,

Error in merger$V1 : $ operator is invalid for atomic vectors

score 85 · Accepted Answer · edited Nov 13 '15 at 23:21

85

You can also name columns directly in the cbind call, e.g.

cbind(date=c(0,1), high=c(2,3))

Output:

     date high
[1,]    0    2
[2,]    1    3

edited Nov 13 '15 at 23:21

arekolek

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answered Apr 01 '14 at 22:37

daknowles

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3

I had the same idea, but somehow only the first column name was used in my case, the subsequent column names were ignored... – Patrick Coulombe Aug 12 '15 at 04:00
4

Try `as.data.frame(cbind(date=c(0,1), high=c(2,3)))`. – Matt May 16 '16 at 19:53

johannes · Answer 2 · 2012-06-19T18:34:52.143

15

Try:

colnames(merger)[1] <- "Date"

Example

Here is a simple example:

a <- 1:10
b <- cbind(a, a, a)
colnames(b)

# change the first one
colnames(b)[1] <- "abc"

# change all colnames
colnames(b) <- c("aa", "bb", "cc")

edited Jun 19 '12 at 18:34

answered Jun 19 '12 at 18:23

johannes

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@ jimsigner I tried that and says: length of 'dimnames' [2] not equal to array extent – janicebaratheon Jun 19 '12 at 18:27
can you provide an reproducible mini example? – johannes Jun 19 '12 at 18:29

score 6 · Answer 3 · answered Aug 11 '12 at 21:36

6

you gave the following example in your question:

colnames(merger)[,1]<-"Date"

the problem is the comma: colnames() returns a vector, not a matrix, so the solution is:

colnames(merger)[1]<-"Date"

answered Aug 11 '12 at 21:36

Marcel Hebing

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score 4 · Answer 4 · answered Jun 19 '12 at 18:29

4

If you pass only vectors to cbind() it creates a matrix, not a dataframe. Read ?data.frame.

answered Jun 19 '12 at 18:29

Roland

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score 4 · Answer 5 · edited May 23 '17 at 12:02

A way of producing a data.frame and being able to do this in one line is to coerce all matrices/data frames passed to cbind into a data.frame while setting the column names attribute using setNames:

a = matrix(rnorm(10), ncol = 2)
b = matrix(runif(10), ncol = 2)

cbind(setNames(data.frame(a), c('n1', 'n2')), 
      setNames(data.frame(b), c('u1', 'u2')))

which produces:

          n1        n2         u1        u2
1 -0.2731750 0.5030773 0.01538194 0.3775269
2  0.5177542 0.6550924 0.04871646 0.4683186
3 -1.1419802 1.0896945 0.57212043 0.9317578
4  0.6965895 1.6973815 0.36124709 0.2882133
5  0.9062591 1.0625280 0.28034347 0.7517128

~~Unfortunately, there is no setColNames function analogous to setNames~~ for data frames that returns the matrix after the column names, however, there is nothing to stop you from adapting the code of setNames to produce one:

setColNames <- function (object = nm, nm) {
    colnames(object) <- nm
    object
}

See this answer, the magrittr package contains functions for this.

score 3 · Answer 6 · answered Jun 19 '12 at 18:34

If you offer cbind a set of arguments all of whom are vectors, you will get not a dataframe, but rather a matrix, in this case an all character matrix. They have different features. You can get a dataframe if some of your arguments remain dataframes, Try:

merger <- cbind(Date =as.character(Date),
             weather1[ , c("High", "Low", "Avg..High", "Avg.Low")] , 
             ScnMov =sale$Scanned.Movement[a] )

score 2 · Answer 7 · answered Jun 18 '17 at 19:18

2

It's easy just add the name which you want to use in quotes before adding vector

a_matrix <- cbind(b_matrix,'Name-Change'= c_vector)

answered Jun 18 '17 at 19:18

Priyansh

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rename the columns name after cbind the data

7 Answers7

Example