[R] Combining Vectors

[Marc Schwartz]

On Wed, 2006-05-17 at 14:58 +0200, Fanie Nel wrote:
> Hi, I'm a new R user, and struggeling with the basics (...sigh)
> 
> I would like to combine 2 vectors :
> 
> d1:
> 
> "S1"   "S2"  "S3"  "S4"
>    1        3       5       6
> 
> 
> and
> 
> 
> d2:
> 
> "S1"    "S3"   "S5"
>    3          3       2
> 
> to give a result:
> 
> "S1"   "S2"  "S3"  "S4"  "S5"
>   1        3        5       6    Na
>   3      Na        3     Na     2
> 
> or better still:
> 
> "S1"   "S2"  "S3"  "S4"  "S5"
>   1        3        5       6       0
>   3         0        3      0       2
> 
> 
> Any ihelp will be appreciated

You want to use the merge() function, which will enable you to perform a
match of the common columns in the two vectors.  Note that the result of
merge() will create a data frame and the column order will be based upon
the common columns first, so in this case S1 and S3:

# Set 'all = TRUE' to include all rows
DF <- merge(d1, d2, all = TRUE)
  
> DF
  S1 S3 S2 S4 S5
1  1  5  3  6 NA
2  3  3 NA NA  2


We can then reorder the columns using names():

DF <- DF[, order(names(DF))]

> DF
  S1 S2 S3 S4 S5
1  1  3  5  6 NA
2  3 NA  3 NA  2


Note that NA has a specific intent in R relative to missing or undefined
values. Setting NA's to 0 may have behavioral impacts that you need to
be aware of depending upon what you intend to do:

# Set NA's in DF to 0
DF[is.na(DF)] <- 0

> DF
  S1 S2 S3 S4 S5
1  1  3  5  6  0
2  3  0  3  0  2

See ?merge, ?order and ?is.na for more information.

HTH,

Marc Schwartz