Repeating a defined function up to n times

Question

I was wondering how I can modify the code below to repeat the function up to 7 times. I can not use replicate(7, func(f)) since I need a function which gives me some option to choose the number of repetitions. I mean, a function which asks me whether I want to continue or not.

suppose

speed<-cars$speed
dist<-cars$dist
level<-c(1:50)   
f<-data.frame(speed,dist,level)
plot(speed, dist, main="Milage vs. Car Weight", 
    xlab="Weight", ylab="Mileage", pch=18, col="blue")
text(speed, dist, row.names(f), cex=0.6, pos=4, col="red")

This is my function

func = function(A){
id.co1 <- identify(f$speed, f$dist,labels=row.names(f), n = 2, pos = TRUE,plot = TRUE)
xy <- f[c(id.co1$ind[1],id.co1$ind[2]),]
lines(xy, col="red", lwd=5)
lm(dist~speed, xy)
abline(coef(lm(dist~speed, xy)),col="blue") 
x.co1 <- f$speed[id.co1$ind[1]:id.co1$ind[2]]
y.co1 <- f$dist[id.co1$ind[1]:id.co1$ind[2]]
m.co1 <- lm(y.co1 ~ x.co1)
}

While it seems you have a reproducible example, `cars` is unknown. Try it yourself in an empty R script. — Parfait, May 04 '17 at 01:59
@Parfait, run require(stats); require(graphics) then you will have access to cars data set. — Marco, May 04 '17 at 02:17
Are you sure? Those are base packages and should already be available. Please update your code with all relevant `library` or `require` lines and object assignment. Test reproducibility in a clean, new R environment. See this often [cited post](http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example). — Parfait, May 04 '17 at 12:31
@Parfait `cars` is in the `datasets` package and gets attached automatically. I cannot reproduce your "`cars` is unknown either in RStudio or in a console. — Janna Maas, May 04 '17 at 12:57
Yes, I can run this code, but I don't understand `func`'s `A` argument. It doesn't appear to be used anywhere in the function. — BLT, May 04 '17 at 14:46
@BLT i kicked it out in my answer, it doesn't seem to have any purpose. — Janna Maas, May 04 '17 at 16:56

Janna Maas · Accepted Answer · 2017-05-04T17:27:34.950

if i understand correctly, you want to specify how often to repeat execution of a function interactively, not programmatically. You can do this with readline:

I need a function which gives me some option to choose the number of repetitions

# some function
funcA <- function(){
 cat("i am funcA\n")
}
# some function that interactively repeats funcA a specified amount of times
doNTimesA <- function() {
  Ntimes <- readline("number of repeats: ")
  for (i in 1:Ntimes) funcA()
}
doNTimesA()

I mean, a function which asks me whether I want to continue or not

funcB <- function(){
  while (TRUE) {
  cat("i am funcB\n")
  continue <- readline("again? y/n: ")
  if (tolower(continue)=="n") break
  }
  cat("funcB is done")
}
funcB()

edit: for your specific case, you can wrap your function declaration in a while loop that asks you whether you want to continue, as in my example funcB above. updated where it also stores its output:

func <- function(){
#initiate an iteration counter and an outputlist
  counter <- 1
  output <- list()
#start an infinite loop
  while (TRUE) {
#do your thing       
    id.co1 <- identify(f$speed, f$dist,labels=row.names(f), n = 2, pos = TRUE,plot = TRUE)
    xy <- f[c(id.co1$ind[1],id.co1$ind[2]),]
    lines(xy, col="red", lwd=5)
    lm(dist~speed, xy)
    abline(coef(lm(dist~speed, xy)),col="blue") 
    x.co1 <- f$speed[id.co1$ind[1]:id.co1$ind[2]]
    y.co1 <- f$dist[id.co1$ind[1]:id.co1$ind[2]]
    m.co1 <- lm(y.co1 ~ x.co1)
#store the result at counter index in the outputlist
    output[[counter]] <- list(xco =x.co1, yco=y.co1, lm =m.co1)
    counter <- counter+1
#prompt for next iteration
    continue <- readline("again? y/n: ")
#break the loop if the answer is 'n' or 'N'
    if (tolower(continue)=="n") break

  }
#return your output
  output
}

What happens now is that after every iteration, the function asks if you want to rerun the function: continue <- readline("again? y/n: ") and checks whether you have answered N or n. You can add more checks on the answer if you like; if you answer anything but N or n now, the loop will run again.

If you run all <- func(), after you're done you can access each iterations' result using all[[1]], all[[2]], etc.

Please note that it's generally frowned upon to manipulate objects outside your function environment, so it would be cleaner to pull the initial plot generation into your function.

Thanks so much for your help, I am a little bit confused about this solution. I want to select different intervals (points) by mouse clicking. What I want is after selecting each two points and connecting them by a straight line, the system asked me whether I want to continue and choose another pair of points. if I say yes then I could select another two points and if I say not the system would give me the value of my last two selection. — Marco, May 04 '17 at 12:50
func is a function which I made and I want to repeat it based on number of the times which I want (by answering yes or not to whether I want to continue or not) — Marco, May 04 '17 at 12:50
the small example is to show how to go about adding a "do you want to continue" option to a function, or to add a "i want to specify how often i want to do this" option. — Janna Maas, May 04 '17 at 13:04
@ Janna Maas, great, thanks so much, just the last question, how can I bring all the results from different repetitions *id.co1* in one matrix. — Marco, May 04 '17 at 15:14
@ Janna Maas, thanks so much for your help. I am really grateful for that. I have another question which I will post it soon. It would be great if you could please provide some answer for that too. It would be similar to this post. — Marco, May 04 '17 at 17:56
@ Janna Maas, could you please provide some answer for this question too http://stackoverflow.com/questions/43789852/modifying-the-code-deleting-a-line-from-the-plot — Marco, May 04 '17 at 18:03

Repeating a defined function up to n times

1 Answers1