Merging two data frames, but keeping NAs

Hi,
Try ?join() 

library(plyr)
y$ref <- y$id

join(x,y,by="ref")

?? ref id val
1?? NA NA? NA
2?? NA NA? NA
3?? NA NA? NA
4?? 10 NA? NA
5??? 9? 9 106
6??? 8? 8 107
7??? 7? 7 105
8??? 6? 6 104
9??? 5 NA? NA
10? NA NA? NA
11?? 1 NA? NA
12?? 2? 2 101
13?? 3? 3 102
14?? 4? 4 103
15?? 5 NA? NA


A.K.

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Hi

My brain is giving up on this...

I have the following two data.frames:

? x <-? data.frame(ref=c(NA, NA, NA, 10:5, NA, 1:5))
? y <-? data.frame(id = c(2, 3, 4, 6, 7, 9, 8), val = 101:107)

Which look as follow:

x

?  ref
1?  NA
2?  NA
3?  NA
4?  10
5? ? 9
6? ? 8
7? ? 7
8? ? 6
9? ? 5
10? NA
11?  1
12?  2
13?  3
14?  4
15?  5

y

? id val
1? 2 101
2? 3 102
3? 4 103
4? 6 104
5? 7 105
6? 9 106
7? 8 107

Now I want to merge y into x, but that

a) the sort order of x stays the same (sort=FALSE in merge()) and
b) the NAs stay

The result should look as follow (column id only here for clarity):

result

?  ref? id? val
1?  NA? NA? NA
2?  NA? NA? NA
3?  NA? NA? NA
4?  10? NA? NA
5? ? 9?  9?  106
6? ? 8?  8?  107
7? ? 7?  7?  105
8? ? 6?  6?  104
9? ? 5? NA? NA
10? NA? NA? NA
11?  1? NA? NA
12?  2?  2? 101
13?  3?  3? 102
14?  4?  4? 103
15?  5? NA? NA

merge(x, y, by.x="ref", by.y="id", sort=FALSE) leaves out the NA, but
otherwise it works:

merge(x, y, by.x=1, by.y="id", sort=FALSE)

? ref val
1?  9 106
2?  8 107
3?  7 105
4?  6 104
5?  2 101
6?  3 102
7?  4 103

Is there any way that I can tell merge() to keep the NA, or how can I
achieve what I want?

Thanks,

Rainer

- -- 
Rainer M. Krug, PhD (Conservation Ecology, SUN), MSc (Conservation
Biology, UCT), Dipl. Phys. (Germany)

Centre of Excellence for Invasion Biology
Stellenbosch University
South Africa

Tel :? ? ?  +33 - (0)9 53 10 27 44
Cell:? ? ?  +33 - (0)6 85 62 59 98
Fax :? ? ?  +33 - (0)9 58 10 27 44

Fax (D):? ? +49 - (0)3 21 21 25 22 44

email:? ? ? Rainer at krugs.de

Skype:? ? ? RMkrug
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