[R] Create macro_var in R

Amoy Yang amoy_y at yahoo.com
Wed Feb 3 19:23:12 CET 2016

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

Duncan Murdoch

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