[R] Create macro_var in R

[Jeff Newmiller]

Are you perhaps needing to (re-)read the discussion on indexing in the "Introduction to R" document that comes with the software? (That is a common deficiency...)

It looks to me like you want something like

MVAR <- "population"
tab[[ MVAR ]]

-- 
Sent from my phone. Please excuse my brevity.

On February 3, 2016 10:23:12 AM PST, Amoy Yang via R-help <r-help at r-project.org> wrote:
>population is the field-name in data-file (say, tab). MVAR<-population
>takes data (in the column of population) rather than field-name as done
>in SAS:  %let MVAR=population;
>In the following r-program, for instance, I cannot use ...
>tab$MVAR...or simply MVAR itself since MVAR is defined as "population"
>with double quotes if using MVAR<-c("population") 
>
>On Wednesday, February 3, 2016 11:54 AM, Duncan Murdoch
><murdoch.duncan at gmail.com> wrote:
> 
>
> On 03/02/2016 12:41 PM, Amoy Yang via R-help wrote:
>>  There is a %LET statement in SAS: %let MVAR=population; Thus, MVAR
>can be used through entire program.
>> In R, I tried MAVR<-c("population"). The problem is that MAVR comes
>with double quote "...." that I don't need. But MVAR<-c(population) did
>NOT work out. Any way that double quote can be removed as done in SAS
>when creating macro_var?
>> Thanks in advance for helps!
>
>R doesn't have a macro language, and you usually don't need one.
>
>If you are only reading the value of population, then
>
>MAVR <- population
>
>is fine.  This is sometimes the same as c(population), but in general 
>it's different:  c() will remove some attributes, such as
>the dimensions on arrays.
>
>If you need to modify it in your program, it's likely more
>complicated.  
>The normal way to go would be to put your code in a function, and have 
>it return the modified version.  For example,
>
>population <- doModifications(population)
>
>where doModifications is a function with a definition like
>
>doModifications <- function(MAVR) {
>    # do all your calculations on MAVR
>    # then return it at the end using
>    MAVR
>}
>
>Duncan Murdoch
>
>
>  
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>
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