# [R] An iterative function

Boris Steipe boris.steipe at utoronto.ca
Mon Oct 30 03:52:19 CET 2017

```Write a for-loop that tests your condition and carries the necessary parameters forward. break() when your condition is met.

B.

> On Oct 29, 2017, at 10:24 PM, li li <hannah.hlx at gmail.com> wrote:
>
> Dear all,
>  The function f() below is a function of m1 and m2, both of which are
> matrices with 3 rows. The function works sequentially one row after
> another.
> So altogether there are three stages. I am trying to update the coding to
> write a generic function that will work for arbitrary k stages.
>  I am hoping to get some suggestion and help. Thanks so much!
>         Hanna
>
>
>
>
> ##x, y are two vectors of the same length
> f0 <- function(x, y){
>  I <- which((x-y)^2>0.5)
>  if (length(I)==0){
>    a <- 0; b <-0; c<- 0
>  } else {
>  a <- min(I)
>  b <- x[a]
>  c <- y[a]}
>  return(list(a=a, b=b, c=c))
> }
>
> ##both m1 and m2 are matrix with 3 rows and same number of columns
> f <- function(m1, m2){
>  n <- dim(m1)
>  tmp1 <- f0(m1[1,], m2[1,])
>  S2 <- which(m1[1,] > tmp1\$a)
>  if (length(S2) == 0){
>    t1 <- c(tmp1\$b, 0, 0)
>    t2 <- c(tmp1\$c, 0, 0)} else {
>    tmp2 <- f0(m1[2,S2], m2[2, (n-length(S2)+1):n])
>    S3 <- S2[which(m2[2, S2] > tmp2\$a)]
>    if (length(S3) == 0) {
>      t1 <- c(tmp1\$b, tmp2\$b, 0)
>      t2 <- c(tmp1\$c, tmp2\$c, 0)} else {
>        tmp3 <- f0(m1[3,S3], m2[3,  (n-length(S3)+1):n])
>        t1 <- c(tmp1\$b, tmp2\$b, tmp3\$c)
>        t2 <- c(tmp1\$c, tmp2\$c, tmp3\$b)
>      }}
>  return(list(t1=t1, t2=t2))
> }
>
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>
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