CODEWITHSUNDEEP
r
Divyansh
Divyansh

Reputation: 166

Can single dimension named vectors be created in R?

I'm trying to name a vector with only a single column, i.e. say I have 

vector<-c(1,2,3,4)

I want to name a single column of (1,2,3,4) as "a", i.e. I want something like:

a
1
2
3
4

If I try

colnames(vector)<- c("a")

It gives me output: 

Error in `colnames<-`(`*tmp*`, value = "a") : 
  attempt to set 'colnames' on an object with less than two dimensions

If I try 

names(vector)<- c("a")

Vector is named as

    a <NA> <NA> <NA> 
   1    2    3    4

My question is if such a vector is allowed in R? Specifically, is this allowed without using a matrix or data.frame or any other such class which can store more than one columns? If yes, how do I create it?

Upvotes: 0

Views: 1306

Answers (1)

IRTFM
IRTFM

Reputation: 263471

If you want something with a column name and that will print in the column format then use a single column matrix or data.frame:

vector <- matrix( c(1,2,3,4), dimnames=list(NULL, "a") )

vector <- data.frame( a=c(1,2,3,4) )

There is a 1d object type but rather confusingly it requires that the assignment of a single dimension value to be its length. See:

  ?dim

dim(vector)=1L
Error in dim(vector) = 1L : 
  dims [product 1] do not match the length of object [4]

> dim(vector)=4L
> vector
[1] 1 2 3 4
> str(vector)
 num [1:4(1d)] 1 2 3 4

Actually the dim function help page doesn't appear to document the requirement that the product of the dim-result will equal the length. My guess is that your homework assignment was intended to get you to read the dim help page and then discover (as I just did) that a one-d object is possible but a bit confusing.

As it turns out the distinction between row and column vectors is not enforced:

> vector %*% matrix(1:16,4)
     [,1] [,2] [,3] [,4]
[1,]   30   70  110  150
> t(vector) %*% matrix(1:16,4)
     [,1] [,2] [,3] [,4]
[1,]   30   70  110  150
> t(vector) %*% matrix(1:16,4) %*% vector
     [,1]
[1,] 1100
> vector %*% matrix(1:16,4) %*% vector
     [,1]
[1,] 1100

Upvotes: 2

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