Using apply with zoo objects

Question

Below is example code of the issue I am having. It seems that zoo does not work with apply. Any suggestions on how to make this work as desired?

> #I am trying to use apply with zoo
> tmp <- zoo(matrix(c(0,1,0,0,0,1),nrow=3))
> tmp

1 0 0
2 1 0
3 0 1
> #for each column I want to subtract the lag
> #as an example I extract 1 column
> tmpcol <- tmp[,1]
> #this is what I want, for each column
> diffcol <- tmpcol-lag(tmpcol,-1)
> diffcol
 2  3 
 1 -1 
> #but if I do this using apply it gives bizarre behavior
> z <- apply(tmp,2,function(x) x-lag(x,-1))
> z
  X.1 X.2
1   0   0
2   0   0
3   0   0

Answer 1

apply coerces its first argument to a plain array so zoo is no longer involved. Perhaps you want this:

> diff(tmp)

2  1 0
3 -1 1

or this

> diff(tmp, na.pad = TRUE)
  x.1 x.2
1  NA  NA
2   1   0
3  -1   1