[R] avoiding expression evaluation when calling a function

[Joshua Wiley]

Hi Benjamin,

See inline

On Fri, Mar 30, 2012 at 12:31 PM, Benjamin Caldwell
<btcaldwell at berkeley.edu> wrote:
> Another question on functions - I have something that looks like
>
> plotter<-function(i){
> temp.i<-rwb[rwb$vector1 <=(i*.10),]
>  with(temp.i, plot(vector2, vector3, main=(i*.10),))
> mod<-lm(vector3~vector3-1,data=temp.i)
>  r2<-summary(mod)$adj.r.squared
> rsqrd[i]<-r2
> legend("bottomright", legend=signif(r2), col="black")
>  abline(mod)
> rsqrd<<-rsqrd
> }
>
>
> I'd rather not have to go into the function and re-type each vector and
> dataframe as I apply it to different vectors. My idea is something like:
>

Close, but pass a formula object.  Something like (untested)


plotter <- function(i, frm, obj, form){
  temp.i<-frm[frm$obj <=(i*.10),]
 plot(form, main=(i*.10), data = temp.i)
  mod<-lm(form, data=temp.i)
 r2<-summary(mod)$adj.r.squared
  legend("bottomright", legend=signif(r2), col="black")
 abline(mod)
 return(rsqrd)
}

and I guess you are doing this for different values of i? so maybe


rsqrd <- lapply(1:100, function(my.i) plotter(i = my.i, frm =
your_frm, obj = your_obj, form = y ~ x))

Hope this helps,

Josh



> plotter<-function(i,frm,obj,x,y){
>  temp.i<-frm[frm$obj <=(i*.10),]
> with(temp.i, plot(x, y, main=(i*.10),))
>  mod<-lm(y~x-1,data=temp.i)
> r2<-summary(mod)$adj.r.squared
> rsqrd[i]<-r2
>  legend("bottomright", legend=signif(r2), col="black")
> abline(mod)
>  rsqrd<<-rsqrd
> }
>
> However, it seems that when I do this the function is calling x, y from the
> global environment rather than simply passing the text and using the frame
> temp.i I create in the function. One idea I had was to go from read.csv to
> frm, obj entirely within the function, but that's about 110 lines of code
> each time.
>
> I'm hoping there's a way to have some of the expressions passed within the
> function without evaluation, in this case without calling data from the
> global environment.
>
> I've tried substitute(),
>
> plotter<-function(i,frm,obj,x,y){
> temp.i<-frm[frm$obj <=(i*.10),]
> with(temp.i, plot(substitute(x), substitute(y), xlim=c(0,250),
> ylim=c(0,35), main=(i*.10),))
>  mod<-lm(substitute(y)~substitute(x)-1,data=temp.i)
> r2<-summary(mod)$adj.r.squared
>  rsqrd[i]<-r2
> legend("bottomright", legend=signif(r2), col="black")
>  abline(mod)
> rsqrd<<-rsqrd
> }
> but am told "cannot coerce type 'symbol' to vector of type 'double'"
>
>
> Any suggestions appreciated.
>
> Thanks
>
> Ben
>
>        [[alternative HTML version deleted]]
>
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-- 
Joshua Wiley
Ph.D. Student, Health Psychology
Programmer Analyst II, Statistical Consulting Group
University of California, Los Angeles
https://joshuawiley.com/