# Problem with apply list to function: numerical expression has 4 elements: only the first used

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## Problem with apply list to function: numerical expression has 4 elements: only the first used

 Hello , I want to try R for statistics. Therefore, I defined a function f with parameters m and k, which calculates a to sqrt(x) proportional density function: f <- function(m,k)((1/(sum(sqrt(1:m))))*sqrt(k)) A function F sums the results in order to get a distribution function: F <- function(m,i)(sum(f(m,1:i))) It works e.g. for m=4: > F(4,1) [1] 0.1627005 > F(4,4) [1] 1 If I want to see all results for m=4, I write > F(4,1:4) [1] 0.1627005 Warning message: In 1:i : numerical expression has 4 elements: only the first used what does the error message mean? and how can I solve it? I've already tried rapply but I get the same error and googled for a while but there is nowhere a satisfying answer Can someone help me here? many thanks in advance, Narua
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## Re: Problem with apply list to function: numerical expression has 4 elements: only the first used

 Dear Narua, Others might suggest other things but here are some of my points. In general it is not a good idea to call a function F as it is an abbreviation for FALSE. Also it might be a good idea to write your functions in a way that they check the length of the arguments and behave accordingly  (if nothing else, with loops). It is really nice to take a look at the family of apply functions (although I also have problems with them sometimes). I did not check, but you can try something like this ff <- function(m,k)((1/(sum(sqrt(1:m))))*sqrt(k)) FF <- function(m,i)(sum(ff(m,1:i))) x <- 1:4 sapply(x, ff, m=4) sapply(x, FF, m=4) Keep up with using R! :) Best, kd ________________________________________ Feladó: R-help [[hidden email]] ; meghatalmazó: Narua [[hidden email]] Küldve: 2015. május 24. 0:21 To: [hidden email] Tárgy: [R] Problem with apply list to function: numerical expression has 4 elements: only the first used Hello , I want to try R for statistics. Therefore, I defined a function f with parameters m and k, which calculates a to sqrt(x) proportional density function: f <- function(m,k)((1/(sum(sqrt(1:m))))*sqrt(k)) A function F sums the results in order to get a distribution function: F <- function(m,i)(sum(f(m,1:i))) It works e.g. for m=4: > F(4,1) [1] 0.1627005 > F(4,4) [1] 1 If I want to see all results for m=4, I write > F(4,1:4) [1] 0.1627005 Warning message: In 1:i : numerical expression has 4 elements: only the first used what does the error message mean? and how can I solve it? I've already tried rapply but I get the same error and googled for a while but there is nowhere a satisfying answer Can someone help me here? many thanks in advance, Narua -- View this message in context: http://r.789695.n4.nabble.com/Problem-with-apply-list-to-function-numerical-expression-has-4-elements-only-the-first-used-tp4707588.htmlSent from the R help mailing list archive at Nabble.com. ______________________________________________ [hidden email] mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code. ______________________________________________ [hidden email] mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: Problem with apply list to function: numerical expression has 4 elements: only the first used

 Dear kd, thanks for your fast reply :-D hm, I thougth, F is normally the abbrevation, but in R FALSE represents "false"? Anyway, your function works. I had actually a little more complicate functions (put I posted in the forum first an easier example): f<-function(a,b)((1/(sum(sqrt(1:a))))*sqrt(b)) F<-function(a,b)(sum(f(a,1:b))) > F(5,3) [1] 0.4946433 > F(5,5) [1] 1 therefore, 0.4946433 is the distribution of b=3 with a=5 Elements. FInv<-function(s,a,b) if(isTRUE(all.equal(F(a,b),s, tolerance=0.00001))) cat("F(",s,",",a,",",b,") equals s; ") else cat("F(",a,",",b,") does not equal to s; ") FInv is the reverse function. you put a probability in the function and recieve the distribution b of a special a. I wanted to have a function FInv' to pass on s for all a and all b to FInv(s,a,b) in order to find out, which probability fits to which a and b. And I couln't pass on a and b so easily, I got the error: "In 1:i : numerical expression has 4 elements: only the first used " I think, the reason is, that R expects a number, but receives a list, and that produces the error. I tried >x<-c(1:10) > FooInv<-function(s) foreach(i=1:10)%do%sapply(x,FInv,s=s,k=i) and that works:> FooInv(0.4946433) F(s = 0.4946433 ,m = 5 ,k = 3 ) equals s; [[1]] Foreach is a for-loop, and sapply matches FInv for every element of the list x. But now another problem occured:Obviously R gets anywhere a NULL-pointer, because the full output is: F(s = 0.4946433 ,m = 5 ,k = 3 ) equals s; [[1]] [[1]][[1]] NULL [[1]][[2]] NULL [[1]][[3]] NULL [[1]][[4]] NULL [[1]][[5]] NULL ... in every loop. Do you know how I can get rid of the NULL-outputs?if this problem is solved, I have all I need in order to calculate the distribution and its inverse function :-) Thanks in advance, Narua