[R] using "rollapply" to calculate a moving sum or running sum?

[Anika Masters]

#using "rollapply" to calculate a moving sum or running sum?

#I am tryign to use rollapply to calcualte a moving sum? #I tried
rollapply and get the error message
#"Error in seq.default(start.at, NROW(data), by = by) :
#  wrong sign in 'by' argument"

#example:

mymatrix <- ( matrix(data=1:100, nrow=5, ncol=20) )
mymatrix_cumsum  <- ( matrix(data=NA, nrow=5, ncol=20) )
w=12
for(i in 1: (ncol(mymatrix)-w+1) ) {
mymatrix_cumsum[ , i]  <- apply(X=mymatrix[, i:(i+w-1)] , MARGIN=1,
FUN=sum, na.rm=T)
}

#How might I use the "rollapply" function instead?

rollapply(mymatrix, 12, sum)

rollapply(data = mymatrix, width = 12, FUN=sum, by.column =T, fill =
NA, partial = FALSE, align = "left" )