Combining vectors of unequal length into a data frame

Question

I have a list of vectors which are time series of inequal length. My ultimate goal is to plot the time series in a ggplot2 graph. I guess I am better off first

Answer 1

If you're doing it just because ggplot2 (as well as many other things) like data frames then what you're missing is that you need the data in long format data frames. Yes, you just put all of your response variables in one column concatenated together. Then you would have 1 or more other columns that identify what makes those responses different. That's the best way to have it set up for things like ggplot.

Answer 2

I think that you may be approaching this the wrong way:

If you have time series of unequal length then the absolute best thing to do is to keep them as time series and merge them. Most time series packages allow this. So you will end up with a multi-variate time series and each value will be properly associated with the same date.

So put your time series into zoo objects, merge them, then use my qplot.zoo function to plot them. That will deal with switching from zoo into a long data frame.

Here's an example:

> z1 <- zoo(1:8, 1:8)
> z2 <- zoo(2:8, 2:8)
> z3 <- zoo(4:8, 4:8)
> nm <- list("z1", "z2", "z3")
> z <- zoo()
> for(i in 1:length(nm)) z <- merge(z, get(nm[[i]]))
> names(z) <- unlist(nm)
> z
  z1 z2 z3
1  1 NA NA
2  2  2 NA
3  3  3 NA
4  4  4  4
5  5  5  5
6  6  6  6
7  7  7  7
8  8  8  8
> 
> x.df <- data.frame(dates=index(x), coredata(x))
> x.df <- melt(x.df, id="dates", variable="val")
> ggplot(na.omit(x.df), aes(x=dates, y=value, group=val, colour=val)) + geom_line() + opts(legend.position = "none")

Answer 3

You can't. A data.frame() has to be rectangular; but recycling rules assures that the shorter vectors get expanded.

So you may have a different error here -- the data that you want to rbind is not suitable, maybe ? -- but is hard to tell as you did not supply a reproducible example.

Edit Given your update, you get precisely what you asked for: a list of names gets combined by rbind. If you want the underlying data to appear, you need to involve get() or another data accessor.