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rxts
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Reputation: 1545

R setting column name on do.call(rbind)

In summary, I am looking to add a cumulative volume column to an XTS object. However, upon calling do.call(rbind... I find the original XTS gets overwritten.

# Reproducible example data
foo <- rnorm(5)
bar <- seq(as.Date("1970-01-01"), length = 5, by = "days")
foobar <- xts(x = foo, order.by = bar)
names(foobar)[1] <- "Volume"
# My processing ...
foobar_months <- split(foobar[,"Volume"],f="months")
foobar_vol_mtd <- lapply(foobar_months,FUN=cumsum)
# This is what is not working for me because Volume overwrites original Volume
foobar <- do.call(rbind,foobar_vol_mtd)

Upvotes: 0

Views: 1026

Answers (1)

R. Schifini
R. Schifini

Reputation: 9313

The function do.call(rbind, list) will do an rbind of all the list elements. You are not appending that list to the original. What you could do is:

foobar2 <- do.call(rbind,foobar_vol_mtd)
foobar <- rbind(foobar, foobar2)

rbind all elements in that list together and then rbind the result to the original.

Result:

               Volume
1970-01-01  0.8995890
1970-01-01  0.8995890
1970-01-02 -0.5057975
1970-01-02  0.3937916
1970-01-03 -0.1861275
1970-01-03  0.2076641
1970-01-04 -1.1641303
1970-01-04 -0.9564663
1970-01-05  0.3157536
1970-01-05 -0.6407127

Results will vary because of rnorm(5) and no seed set.

Append as new columns

As I said, rbind appends new rows and all columns should be the same. If you want to append as a new column then try:

foobar2 <- do.call(rbind,foobar_vol_mtd)
foobar3 = merge(foobar, foobar2)

My result for this case is (new random values, so don't compare to above):

                Volume  Volume.1
1970-01-01  1.96291153 1.9629115
1970-01-02 -0.41771710 1.5451944
1970-01-03 -0.08827657 1.4569179
1970-01-04 -0.57243569 0.8844822
1970-01-05 -0.06093953 0.8235426

Then change the column name with names(foobar)[2] = "new_name".

You could also rename before the merge:

foobar2 <- do.call(rbind,foobar_vol_mtd)
names(foobar2) = 'newname'
foobar3 = merge(foobar, foobar2)

And the merge will be done by the time index as before.

Upvotes: 1

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