Hello there,

I am trying to compute the 3 months return momentum with the timeSeries x.ts, 
which is just a subset of simple returns from a much bigger series,

> class(x.ts)
[1] "timeSeries"
attr(,"package")
[1] "timeSeries"

> dim(x.ts)
[1] 20  3

> x.ts[1:8,]
GMT
                 MS.US      AAPL.US       CA.FP
1996-01-31  0.15159065 -0.133391894  0.10602243
1996-02-29 -0.00692633 -0.004488850  0.03986648
1996-03-29  0.06511157 -0.106763636  0.07930919
1996-04-30 -0.04803468 -0.007653477  0.09490285
1996-05-31  0.08715949  0.071709879  0.05126406
1996-06-28 -0.03586503 -0.196141479  0.01908068
1996-07-31 -0.10941283  0.047619048 -0.04993095
1996-08-30 -0.01720023  0.102363636 -0.06605725

Then, I ran the following,

f <- function(xIn) {prod(1 + xIn)}
tmp.ts <- apply.rolling(x.ts[,, drop = FALSE], FUN=f, width=3)
xMom.ts <- tmp.ts - 1

where,

> xMom.ts[1:8,]
GMT
                  calcs
1996-01-31           NA
1996-02-29           NA
1996-03-29  0.218076872
1996-04-30  0.006926330
1996-05-31  0.102324581
1996-06-28 -0.002179951
1996-07-31 -0.066514593
1996-08-30 -0.156122673

It seems that apply.rolling() only executed for the first column "MS.US" but not 
column 2 nor 3.

Q: Apart from looping through the column index manually via a for loop, which is 
not ideal in R, is there any other way to execute the function for every column 
in this setup?

Many thx.

Will 

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