[R] xyplot: superpose 2 time series with different time intervals

Gary Lewis gary.m.lewis at gmail.com
Mon Aug 3 14:22:11 CEST 2009

Thank you Deepayan. Your suggestion worked perfectly.

Thanks too to Gabor for your suggestion and for your help trying to
get this help request through to r-help before I subscribed.

I'm all set now.


On Sat, Aug 1, 2009 at 1:17 PM, Deepayan
Sarkar<deepayan.sarkar at gmail.com> wrote:
> On Sat, Aug 1, 2009 at 7:26 AM, Gary Lewis<gary.m.lewis at gmail.com> wrote:
>> I could use some advice regarding xyplot.
>> I've got 2 time series. Both cover approximately the same period of
>> time (ie, 1940 to 2009). But one series has annual data and the other
>> has monthly data. One refers to university enrollment; the other to
>> unemployment rates. Both are currently in the same data frame.
>> I'd like to use the monthly times series as a light grayscale
>> background for a plot of the annual time series, showing both series
>> as type "l" (line). Naturally with all the NA's in the annual series,
>> that plot disappears because points are not connected across missing
>> values.
> You could define a small wrapper function that discards NA's before
> drawing lines:
> my.panel.lines <- function(x, y, ...) {
>    keep <- !is.na(y)
>    panel.lines(x[keep], y[keep], ...)
> }
> and use it as a custom panel.groups function:
> xyplot(<whatever you had before>,
>       panel = panel.superpose, panel.groups = my.panel.lines)
> -Deepayan
>> I suppose I could make both series annual, but a lot of interesting
>> detail would get lost this way. Or I guess I could interpolate values
>> in the annual series with monthly approximations, but this means 11
>> out of every 12 values is an approximation. Or I suppose I could plot
>> each series separately and then print them with position information,
>> which I'm reluctant to do because panel.superpose so nicely handles
>> the alignment of the 2 panels.
>> What I'd really like to do is plot each independently but still
>> superposed. Effectively this seems to mean monthly data intervals but
>> line connections across the NA's in the series with annual intervals.
>> Any suggestions would be appreciated. Thanks.
>> Gary Lewis
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