R help - Apr 2009 - R Macro Question

Dear all,

I am a new R user, and I have a question about R macro.

Here is the situation, I want to do item option analysis (options include: A
, B, C, D), below is the codes for option A analyses.


#option A analyses

optiona<-mat.or.vec(nrow(responsedata2), ncol(responsedata2))

# create A matrix by recoding
for (i in 1:ncol(responsedata2)){
   
optiona[,i]<-recode(responsedata2[,i],"'A'=1;NA=NA;else=0")
}

# compute mean for A matrix

pa<-rep(0,ncol(optiona))
for (i in 1:ncol(optiona)){
    pa[i]<-round(mean(optiona[,i],na.rm=TRUE),2)
}

pa1<-as.data.frame(pa)
 
I can repeat the codes for other options such as "B", "C"
and "D", but I am wondering if I can do it 
in a macro way--subsituting "A" "a" in the codes with "B" "b", etc.

In SAS it can be done easily, but I could not get it to work in R.

Waiting for your reply.

And thank you so much in advance.

Meng


      
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On Wed, 29 Apr 2009, Jenn wrote:
> Dear all,
>
> I?am?a?new?R?user,?and?I?have?a?question?about?R?macro.
>
>
Here?is?the?situation,?I?want?to?do?item?option?analysis?(options?include:?A
> ,?B,?C,?D),?below?is?the?codes?for?option?A?analyses.
>
>
> #option?A?analyses
>
> optiona<-mat.or.vec(nrow(responsedata2),?ncol(responsedata2))
>
> #?create?A?matrix?by?recoding
> for?(i?in?1:ncol(responsedata2)){
> ???
optiona[,i]<-recode(responsedata2[,i],"'A'=1;NA=NA;else=0")
> }
>
> #?compute?mean?for?A?matrix
>
> pa<-rep(0,ncol(optiona))
> for?(i?in?1:ncol(optiona)){
> ??? pa[i]<-round(mean(optiona[,i],na.rm=TRUE),2)
> }
>
> pa1<-as.data.frame(pa)
> ?
> I?can?repeat?the?codes?for?other?options such as "B",
"C" and "D",?but?I?am?wondering?if?I?can?do?it?
>
in?a?macro?way--subsituting?"A"?"a"?in?the?codes?with?"B"?"b",?etc.
>
> In?SAS?it?can?be?done?easily,?but?I?could?not?get?it?to?work?in?R.
I suspect that 'it' can also be done easily in R.

But you have not really told the list what 'it' is.

You should provide some R code that actually works- as the R Posting Guide 
recommends. The 'code' above is not syntactically valid R, so you
haven't
really run it and neither can we.

The function 'recode' is not in base R, so you have to provide it or
refer
to the contributed package frmo which it is obtained.

I can only guess what you are trying to do, but I'd say mapply() or one of 
its relatives (lapply, tapply, ... ) is probably equal to the type of task 
you wish to perform.


HTH,

Chuck
>
> Waiting?for?your?reply.
>
> And?thank?you?so?much?in?advance.
>
> Meng
>
>
>
> 	[[alternative HTML version deleted]]
>
>
Charles C. Berry                            (858) 534-2098
                                             Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	            UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901