r - cbind: is there a way to have missing values set to NA?

Question

Please forgive me if I missed an answer to such a simple question.

I want to use cbind() to bind two columns. One of them is a single entry shorter in length.

Can I have R supply an NA for the missing value?

The documentation discusses a deparse.level argument but this doesn't seem to be my solution.

Further, if I may be so bold, would there also be a quick way to prepend the shorter column with NA's?

Answer 1

Try this:

x <- c(1:5)
y <- c(4:1)
length(y) = length(x)
cbind(x,y)
     x  y
[1,] 1  4
[2,] 2  3
[3,] 3  2
[4,] 4  1
[5,] 5 NA

or this:

x <- c(4:1)
y <- c(1:5)
length(x) = length(y)
cbind(x,y)
      x y
[1,]  4 1
[2,]  3 2
[3,]  2 3
[4,]  1 4
[5,] NA 5

I think this will do something similar to what DWin suggested and work regardless of which vector is shorter:

x <- c(4:1)
y <- c(1:5)

lengths <- max(c(length(x), length(y)))
length(x) <- lengths
length(y) <- lengths
cbind(x,y)

The code above can also be condensed to:

x <- c(4:1)
y <- c(1:5)
length(x) <- length(y) <- max(c(length(x), length(y)))
cbind(x,y)

EDIT

Here is what I came up with to address the question:

"Further, if I may be so bold, would there also be a quick way to prepend the shorter column with NA's?"

inserted into the original post by Matt O'Brien.

x <- c(4:1)
y <- c(1:5)

first <- 1   # 1 means add NA to top of shorter vector
             # 0 means add NA to bottom of shorter vector

if(length(x)<length(y)) {
     if(first==1) x = c(rep(NA, length(y)-length(x)),x);y=y
     if(first==0) x = c(x,rep(NA, length(y)-length(x)));y=y
} 

if(length(y)<length(x)) {
     if(first==1) y = c(rep(NA, length(x)-length(y)),y);x=x
     if(first==0) y = c(y,rep(NA, length(x)-length(y)));x=x
} 

cbind(x,y)

#       x y
# [1,] NA 1
# [2,]  4 2
# [3,]  3 3
# [4,]  2 4
# [5,]  1 5

Here is a function:

x <- c(4:1)
y <- c(1:5)

first <- 1   # 1 means add NA to top of shorter vector
             # 0 means add NA to bottom of shorter vector

my.cbind <- function(x,y,first) {

  if(length(x)<length(y)) {
     if(first==1) x = c(rep(NA, length(y)-length(x)),x);y=y
     if(first==0) x = c(x,rep(NA, length(y)-length(x)));y=y
  } 

  if(length(y)<length(x)) {
     if(first==1) y = c(rep(NA, length(x)-length(y)),y);x=x
     if(first==0) y = c(y,rep(NA, length(x)-length(y)));x=x
  } 

  return(cbind(x,y))

}

my.cbind(x,y,first)

my.cbind(c(1:5),c(4:1),1)
my.cbind(c(1:5),c(4:1),0)
my.cbind(c(1:4),c(5:1),1)
my.cbind(c(1:4),c(5:1),0)
my.cbind(c(1:5),c(5:1),1)
my.cbind(c(1:5),c(5:1),0)

This version allows you to cbind two vectors of different mode:

x <- c(4:1)
y <- letters[1:5]

first <- 1   # 1 means add NA to top of shorter vector
             # 0 means add NA to bottom of shorter vector

my.cbind <- function(x,y,first) {

  if(length(x)<length(y)) {
     if(first==1) x = c(rep(NA, length(y)-length(x)),x);y=y
     if(first==0) x = c(x,rep(NA, length(y)-length(x)));y=y
  } 

  if(length(y)<length(x)) {
     if(first==1) y = c(rep(NA, length(x)-length(y)),y);x=x
     if(first==0) y = c(y,rep(NA, length(x)-length(y)));x=x
  } 

  x <- as.data.frame(x)
  y <- as.data.frame(y)

  return(data.frame(x,y))

}

my.cbind(x,y,first)

#    x y
# 1 NA a
# 2  4 b
# 3  3 c
# 4  2 d
# 5  1 e

my.cbind(c(1:5),letters[1:4],1)
my.cbind(c(1:5),letters[1:4],0)
my.cbind(c(1:4),letters[1:5],1)
my.cbind(c(1:4),letters[1:5],0)
my.cbind(c(1:5),letters[1:5],1)
my.cbind(c(1:5),letters[1:5],0)