On 03/02/2016 1:23 PM, Amoy Yang 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$MVAR...or simply MVAR itself since MVAR
is defined as "population" with double quotes if using MVAR<-c("population")
In that case, you can use
MVAR <- "population"
and then work with
tab[[MVAR]]
instead of tab$population.
But it would often make more sense to extract that column into a
separate variable, and work with that, either as
MVAR <- tab$population
or
tab$population <- doModifications(tab$population)
following the same patterns as below.
Duncan Murdoch
On Wednesday, February 3, 2016 11:54 AM, Duncan Murdoch
<murdoch.dun...@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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