Color option in xtsExtra

Question

I am having trouble adjusting the colors of a multiple time series plot using xtsExtra.

This is the code of a minimal example:

require("xtsExtra")

n <- 50
data <- replicate(2, rnorm(n))

my.ts <- as.xts(ts(data, start=Sys.Date()-n, end=Sys.Date()))

plot.zoo(my.ts, col = c('blue', 'green')) 
plot.xts(my.ts, col = c('blue', 'green'))

The plot.zoo commands yields

,

whereas the plot command from the xtsExtra package results in

.

In the second plot, the two time series are nicely overlaid, but seem insensitive to the col option.

I'm using the latest version 0.0-1 of the xtsExtra package (rev. 862).

It is my understanding that the xts and xtsExtra packages are designed as extensions of zoo and should work with the same arguments (plus many additional ones). Even though I can get the same overlay behavior in plot.zoo using the screens option, I cannot really resort to using it because the call to plot.xts that causes my problems is within the quantstrat package (functions chart.forward.training and chart.forward.testing for example) which I'd loathe to modify. (Incidentally, the dev.new() in these functions is causing me trouble as well.)

Question: Why does plot from the xtsExtra package seem not to respond to the col= option and what can be done about it, if modifying the call to the function is not a real option?

Answer 1

Q1. If you take time to read the help text for plot.xts, you see that the function does not have a col argument. Together with the fact that partial matching of argument names doesn't seem to be allowed in the function, it explains why plot.xts it does not respond col =.

Compare with a case where partial matching works:
plot(x = 1:2, y = 1:2, type = "b"); plot(x = 1:2, y = 1:2, ty = "b"); "ty" matches "type".
See here: "If the name of the supplied argument matches exactly with the first part of a formal argument then the two arguments are considered to be matched".

Q2. Instead you may use the colorset argument: "color palette to use, set by default to rational choices" (colorset = 1:12).

plot.xts(my.ts, colorset = c('blue', 'green'))