> On Feb 3, 2016, at 11:57 AM, Amoy Yang via R-help <r-help@r-project.org>
> wrote:
>
> Right! the following works to r but not sqldf.
> MVAR <- "population"
> tab[[ MVAR ]]
> sqldf("select tab[[MVAR]] from tab")
If ypu need a string to pass to sqldf, then use the `paste` function to build a
single string:
sqldf( paste("select", MVAR, " from tab") )
--
David.
>
> On Wednesday, February 3, 2016 1:18 PM, Amoy Yang via R-help
> <r-help@r-project.org> wrote:
>
>
> First, MVAR<-c("population) should be the same as "population'". Correct?
> You use tab[[MVAR]] to refer to "population" where double [[...]] removes
> double quotes "...", which seemingly work for r-code although it is tedious
> in comparison direct application in SAS %let MVAR=population. But it does not
> work for sqldef in R as shown below.
>
>> key<-"pop"
>> library(sqldf)
>> sqldf("select grade, count(*) as cnt, min(tab[[key]]) as min,
> + max(pop) as max, avg(pop) as mean, median(pop) as median,
> + stdev(pop) as stdev from tab group by grade")
> Error in sqliteSendQuery(con, statement, bind.data) :
> error in statement: near "[[key]": syntax error
>
>
>
>
> On Wednesday, February 3, 2016 12:40 PM, "ruipbarra...@sapo.pt"
> <ruipbarra...@sapo.pt> wrote:
>
>
> Hello,
>
> You can't use tab$MVAR but you can use tab[[MVAR]] if you do MVAR <-
> "population" (no need for c()).
>
> Hope this helps,
>
> Rui Barradas
> Citando Amoy Yang via R-help <r-help@r-project.org>:
> population is the field-name in data-file (say, tab). MVAR<-population takes
> data (in the column of population) rather than field-name as done in SAS:
> %let MVAR=population;
> In the following r-program, for instance, I cannot use ... tab$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.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
>
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
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> self-contained, reproducible code.
>
>
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>
> [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
David Winsemius
Alameda, CA, USA
______________________________________________
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