Re: [R] Pointwise division of two zoo objects?

From: Kenn Konstabel <lebatsnok_at_gmail.com>
Date: Tue, 15 Mar 2011 11:02:50 +0200

Hi,

> returns.z = tail(prices.z,-1)/head(prices.z,-1) - 1 # should be equivalent
> to returns = exp(diff(log(prices.z))) - 1
>
> Curiously, I get a zoo object back with zeros everywhere and also with the
> index having one fewer element than it should.
>
> Does anyone know how to pointwise divide zoo objects, and what exactly "/"
> is doing?
>

I think any arithmetic operations on zoo objects work on values having the same indexes. So if

x <- zoo(1:10, 1:10)
y <- zoo(1:10, 11:20)
x/y
# no result as no elements have the same index y <- zoo(1:10, 6:15)
x/y
# last five elements from x, first five from z

To do your first example, you can use coredata so that one of your obejcts would be an ordinary vector:

returns.z = tail(prices.z,-1)/coredata(head(prices.z,-1)) - 1

Regards,

Kenn

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