[R] R lappy, sapply or mapply question

Adams, Jean
2015-10-09T21:56:15Z

You were very close.  Try this.

df <- data.frame(x5=dailyrecord$a, x6 = dailyrecord$e, x7 = dailyrecord$f)
apply(df, 1, function(row) fun3(list1, list2, as.list(row)))

Jean

On Fri, Oct 9, 2015 at 3:15 PM, liqunhan--- via R-help <r-help at
r-project.org
> wrote:

>
>
> Hello, R-experts,
> In R-program, I have a question about the apply-family.
> I want to use apply-family to replace a for-loop in my R-code,But, lapply
> returns a list of 3 (each component is the same), sapply returns a matrix,
> and mapply with error message.
> how to use apply-family function so that it returns a vector, as it does
> when using for-loop in my R-codes below?
> Hope to hear back soon!
> Thank you very much!
>
>
>
> #-------------------------------------------------------------------------
> # Below is my R-codes:
> #-----------  begin of  R code --------------------------------------
> # suppose list1 returned by fun1()
> # fun1() is a R-script with about 200 lines
> list1 <- list(u=3.8, v=53.42)# suppose list2 returned by fun2()
> # fun2() is a R-script with about 5000 lines
> list2 <- list(x=3.8, y=-9,3)# demo fun3(), the actual function is much
> more complicated
> fun3 <- function(xlist1, xlist2, xlist3) {
>
>   x1 <- xlist1$u
>   x2 <- xlist1$v
>
>   x3 <- xlist2$x
>   x4 <- xlist2$y
>
>   x5 <- xlist3$x5
>   x6 <- xlist3$x6
>   x7 <- xlist3$x7
>
>   w <- x1^2 + sqrt(x2+x3) - 0.75*x4 + exp(x5)
>   z <- sin(x2)/x7 + x6/(x3+x4)
>   return(w+z)
> }dailyrecord <- data.frame(a = rnorm(50000), b = rnorm(50000), c >
rnorm(50000),
>                           d = rnorm(50000), e = rnorm(50000), f >
rnorm(50000),
>                           g = rnorm(50000))
> result_forloop <- rep(0, 50000)
> # use for - loop ## how to avoid the for-loop ??for (k in 1 : 50000) {
>   xlist <- list(x5 = dailyrecord$a[k], x6 = dailyrecord$e[k], x7 >
dailyrecord$f[k])
>   result_forloop[k] <- fun3(list1, list2, xlist)
> }# use lapply  #--- return a list of 3 ------------
> xlst <- list(x5=dailyrecord$a, x6 = dailyrecord$e, x7 = dailyrecord$f)
> result_lapply <- lapply(xlst, function(s) fun3(list1, list2, xlst))
>
> # use sapply  #--- return a matrix  -------
> result_sapply <- sapply(xlst, function(s) fun3(list1, list2, xlst))
>
> # use mapply  #--- error  -------
> result_mapply <- mapply(fun3, xlist1 = list1, xlist2 = list2, xlist3
> xlst)
>
> #-----------  end of R code --------------------------------------
>
>
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>
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