Convert a matrix to an xts object

Question

I am new to R and need to use the function getnfac from the PANICr package. And it seems that the function only takes an xts object as its first argument. However, after I went through some reading I still don't understand what an xts object is. Could anyone please tell me how I can convert a matrix into an xts object?

Below I use return matrix as the first argument. Therefore I just need to convert return to an xts object.

getnfac(return,143,"BIC3")
Error in getnfac(return, 143, "BIC3") : 
  x must be an xts object so lags and differences are taken properly

Answer 1

xts is an extensible time series object, essentially a regular ts object (or more correctly a zoo object) with some bits added.
The 'extensible' part of the name refers to how you can add attributes of your own choice.

While a matrix can be converted into a multivariate time series quite easily

m <- matrix(1:16, 4)
m.ts <- ts(m)
index(m.ts)

An xts requires its index (a vector describing at what time each sample was taken) to be in a date or time format

library(xts)
m <- matrix(1:16, 4)
d <- as.Date(1:nrow(m))
m.xts <- xts(m, order.by=d)
index(m.xts)

If your data is sampled at evenly spaced intervals a dummy index like the one above is probably ok. If not, you'll need to supply a vector corresponding to the sampling times.

Answer 2

In my opinion, the first argument to the getnfac() function should be matrix containing the data.

In addition to the above answers, You can convert matrix format using coredata() about xts object.