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Create macro_var in R

13 messages · Amoy Yang, Henrik Bengtsson, Duncan Murdoch +6 more

Original
Amoy Yang
# 
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!
Amoy
Henrik Bengtsson
# 
Don't know what `population` is, but a simple assignment

MVAR <- population

may provide what you need.  Note, no c().  For example,
[1] -0.08093862 -0.87827617  1.52826914

/Henrik

On Wed, Feb 3, 2016 at 9:41 AM, Amoy Yang via R-help
<r-help at r-project.org> wrote:
Duncan Murdoch
#
On 03/02/2016 12:41 PM, Amoy Yang via R-help wrote:
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
Amoy Yang
# 
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:

            

      
      
      
    

        
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

  
  


  


      

    

    

      
      

        


  

        

      Duncan Murdoch
    

    

      
      #
    

  


  

      
On 03/02/2016 1:23 PM, Amoy Yang wrote:

            

      
      
      
    

        
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

            

      
      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Bert Gunter
    

    

      
      #
    

  


  

      
I am not sure what you want, but:

1) If you have not already done so, go through an R tutorial or two.
For some suggestions:

https://www.rstudio.com/resources/training/online-learning/#R

 R is quite different than SAS.

2) If I misunderstand, perhaps

?within

is what you are looking for.

Cheers,
Bert
Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Wed, Feb 3, 2016 at 10:23 AM, Amoy Yang via R-help

        
<r-help at r-project.org> wrote:

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        


  

        

      Rui Barradas
    

    

      
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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 at r-project.org>:

            

      
      
      
    

        

      
      
    

        
?

  
  


  


      

    

    

      
      

        


  

        

      Jeff Newmiller
    

    

      
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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 ]]

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Amoy Yang
    

    

      
      #
    

  


  

      
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.

            

      
      
      
    

        
+ 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, "ruipbarradas at sapo.pt" <ruipbarradas at 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 at 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.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



? ? ? ? [[alternative HTML version deleted]]

______________________________________________
R-help at 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.htmland provide commented, minimal, self-contained, reproducible code.

?

  
  


  


      

    

    

      
      

        


  

        

      MacQueen, Don
    

    

      
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Repeat many times:   R does not work the same way as SAS, do not expect it
to

If I needed to construct an SQL statement in which the name of a field is
provided by the value of another variable, I would consider this:

key <- 'pop'
sql.stmt <- paste("select grade,
 count(*) as cnt,
 min(",key,") as min,
 max(",key,") as max,
 avg(",key,") as mean,
 median(",key,") as median,
 stdev(",key,") as stdev
from tab
group by grade"

)

Then
  print(sql.stmt, quote=FALSE)
to make sure I got what I wanted.

Use paste0() instead of paste() if you don't want the extra space
characters, even though they don't matter to SQL.

And, no, the double [[...]] does not remove double quotes. That's not how
it works.
  tab[['pop']]
  tab[ , 'pop']
  tab$pop
are three different ways to reference the pop column in the tab data
frame. Of the three, the value 'pop' can be stored in a variable with the
first two, but not the third one.

Remember, R is not SAS, so you have to use a different technique to
construct the desired SQL statement; there is nothing in R that works
exactly like SAS macro variables. (R has other advantages).

-Don

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Amoy Yang
    

    

      
      #
    

  


  

      
Right! the following works to r but not sqldf.
MVAR <- "population"
 tab[[ MVAR ]]
sqldf("select tab[[MVAR]] from tab")

        
On Wednesday, February 3, 2016 1:18 PM, Amoy Yang via R-help <r-help at 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.

            

      
      
      
    

        
+ 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, "ruipbarradas at sapo.pt" <ruipbarradas at 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 at 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.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



? ? ? ? [[alternative HTML version deleted]]

______________________________________________
R-help at 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.htmlandprovide commented, minimal, self-contained, reproducible code.

?

? 
??? [[alternative HTML version deleted]]

______________________________________________
R-help at 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
    

    

      
      #
    

  


  

          

      
      
      
    

        
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") )

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      Gabor Grothendieck
    

    

      
      #
    

  


  

      
See

  Example 5.  Insert Variables

on the sqldf home page.

  https://github.com/ggrothendieck/sqldf


On Wed, Feb 3, 2016 at 2:16 PM, Amoy Yang via R-help

        
<r-help at r-project.org> wrote: