apply function with multiple arguments and variables

Question

How do I provide multiple parameters and variables to an apply function? I'd like to pass vectir c(1, 2) to argument l and varaibles c(x, x1) to argument k.

Desired Output should have four columns instead of two

Example

library(zoo)
datt <- data.frame(x = rnorm(100),
           x2 = rnorm(100))
mapply(function(l, k) c(rollmean(datt[,k], l), rep(NA, l-1)),
       c(1, 2),
       c("x", "x2"))

Output

           x         x2
1 -0.2688922  0.9506357
2  0.1402062  0.7324266
3  0.1391136 -1.7412695
4  1.4542990  2.1617833
5 -0.9409344  2.0495386
6 -0.8309520  0.6403896

If the l statnds for the 'k' argument, there would be only two column output. — akrun
– akrun, Commented Feb 28, 2018 at 4:29

akrun · Accepted Answer · 2018-02-28 04:31:04Z

2

If we have to apply the 'k' for multiple columns, pass the columns in a list

res <- do.call(cbind, Map(function(l, k) rollmean(datt[,k], l, fill = NA), 
           1:2, list(c("x", "x2"))))

However, we don't an extra argument as the need is for looping the k argument and the subset of data remains the same

do.call(cbind, lapply(1:2, rollmean, x = datt[c("x", "x2")], fill = NA))

answered Feb 28, 2018 at 4:31

akrun

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3 Comments

Vedda Over a year ago

Thanks! However, I need to retain the l-1 because I lag the rollmean by 1.

akrun Over a year ago

@Vedda Ok, then you can remove the fill = NA and use your rep(NA, l-1)

G. Grothendieck Over a year ago

In rollapply the width= can be a one component list containing a vector of offsets. This would avoid the rep. I have shown that in my revised answer but that approach could be incorporated here too.

G. Grothendieck · Accepted Answer · 2018-02-28 13:19:57Z

2

Create a grid 4x2 grid of the 4 combinations of l and k and then mapply over that. Note that we can simplify fun slightly using fill = NA . Note that the width argument of list(1:l) means pass offsets 1 through l to the mean. Offset 1 is the next value and offset 2 is the value after the next value.

fun <- function(l, k) rollapply(datt[, k], list(1:l), mean, fill = NA)
g <- expand.grid(l = 1:2, k = c("x", "x2"))
mapply(fun, g[[1]], g[[2]])

Update

Based on comments by poster clarifying intent changed rollmean to rollapply with indicated width.

edited Feb 28, 2018 at 13:19

answered Feb 28, 2018 at 4:33

G. Grothendieck

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