[R] using chron vector with boxplot

[Gabor Grothendieck]

Try this:

  boxplot(as.matrix(data) ~ as.Date(date), cex.axis = 0.5, las = 2)

or if all the dates are in the same year and month as they are here
then you might want to just display the day of the month:

  boxplot(as.matrix(data) ~ month.day.year(date)$day)


On Sun, May 31, 2009 at 1:45 PM, Kenneth Takagi <kat215 at psu.edu> wrote:
> Hi,
>
>
>
> I'm having trouble using dates (created using library(chron)) as
> groupings for a boxplot.  I have 10 repeat measurements of a variable
> within an individual day.  The measurements were done over 10 days.  I
> would like to plot the measurements as a box and wisker plot (using
> boxplot or something similar) where the days (as chron object) would be
> the grouping and the repeated measurements of the variable make up the
> box and wisker plot.  I would like the spacing of the individual
> boxplots to reflect the time between measurements:
>
>
>
> Example using random numbers:
>
>
>
> ### Create date vector of measurement dates
>
> library(chron)
>
> time=c(39083, 39085, 39095, 39096, 39103, 39104, 39105, 39110, 39113,
> 39120);
>
> orig =chron("01/01/1900")
>
> date = orig + time-2;
>
>
>
> ###  Data for B and W plot
>
> data = data.frame();
>
> mean=rnorm(10, mean=0, sd=1);
>
> for(i in 1:10){data[1:10,i] =rnorm(10, mean=mean[i], sd=1)};
>
>
>
> ### Plot
>
> boxplot(data, range=0);  # works, but doesn't reflect the different time
> intervals between measurements dates!
>
> boxplot(data~date, range=0) # tried using formula, gives error:
>
>            Error in model.frame.default(formula = data ~ date) :
>
>             invalid type (list) for variable 'data'
>
>
>
> Not sure what to try next.  Any suggestions?
>
>
>
> Thanks,
>
> ken
>
>
>
> kat215 at psu.edu
>
>
>
>
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>
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