More complex time-series objects

The main limitation of the ts time-series R object class (besides the aforementioned x axis issue) is that it cannot deal with irregular time-series. To overcome this problem, we have several alternatives in R.

The zoo package and its reverse dependent xts packages are ts-compatible classes with tons of extremely useful methods. For a quick example, let's build a zoo object from our data, and see how it's represented by the default plot:

> library(zoo)
> zd <- zoo(daily[, -1, with = FALSE], daily[[1]])
> plot(zd)

As we have defined the date column to act as the timestamp of the observations, it's not shown here. The x axis has a nice human-friendly date annotation, which is really pleasant after having checked a bunch of integer-annotated plots in the previous pages.

Of course, zoo supports most of the ts methods, such as diff, lag or cumulative sums; these can be very useful for visualizing data velocity:

> plot(cumsum(zd))

Here, the linear...