[R] R lappy, sapply or mapply question

liqunhan at yahoo.com
2015-10-09T20:15:16Z

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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