[R] Application of "merge" and "within"

[Jeff Newmiller]

What is complicated about merge( q, r )?

Keep in mind that there is nothing simple about the rules for non-standard evaluation of variables that within() uses, and it only gets more complicated if you try to apply those rules to two data frames at once. While I am not quite sure I understand what you really want, I suspect you won't like the behavior you get when you pile too much context into within(). 

Note that dplyr::inner_join, which is designed to fit into a whole ecosystem of NSE functions, uses strings to specify column names to join by just like the merge "by" parameters do rather than using NSE, because it is actually the least confusing approach when two data frames are being referenced. 
-- 
Sent from my phone. Please excuse my brevity.

On May 31, 2016 10:50:24 AM PDT, Santosh <santosh2005 at gmail.com> wrote:
>Thanks for response.. I want to merge two data frames using "within"
>function..the columns to used for merge could vary.. then the other
>commands become simpler..
>
>Thanks so much for your help!
>Santosh
>
>On Sat, May 28, 2016 at 1:53 PM, Duncan Murdoch
><murdoch.duncan at gmail.com>
>wrote:
>
>> On 27/05/2016 7:00 PM, Santosh wrote:
>>
>>> Dear Rxperts!
>>>
>>> Is there a way to compute relative values.. using within()..
>function?
>>>
>>> Any assistance/suggestions are highly welcome!!
>>> Thanks again,
>>> Santosh...
>>> ___________________________________________________________________
>>> A sample dataset and the computation "outside" within()  function is
>>> shown..
>>>
>>> q <- data.frame(GL = rep(paste("G",1:3,sep = ""),each = 50),
>>>                 G  = rep(1:3,each = 50),
>>>                 D = rep(paste("D",1:5,sep = ""),each = 30),
>>>                 a = rep(1:15,each = 10),
>>>                 t = rep(seq(10),15),
>>>                 b = round(runif(150,10,20)))
>>> r <- subset(q,!duplicated(paste(G,a)),sel=c(G,a,b))
>>> names(r)[3] <- "bl"
>>> s <- merge(q,r)
>>>  s$db <- s$b-s$bl
>>>
>>> head(s,5)
>>>>
>>>     G  a GL  D  t  b bl db
>>> 1   1  1 G1 D1  1 13 13  0
>>> 2   1  1 G1 D1  2 16 13  3
>>> 3   1  1 G1 D1  3 19 13  6
>>> 4   1  1 G1 D1  4 12 13 -1
>>> 5   1  1 G1 D1  5 19 13  6
>>>
>>
>> Just use
>>
>>  s <- within(s, db <- b - bl)
>>
>> Duncan Murdoch
>>
>>
>
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