[R] lattice barchart() with two variables

Rich Shepard r@hep@rd @end|ng |rom @pp|-eco@y@@com
Wed Aug 22 20:18:34 CEST 2018

On Wed, 22 Aug 2018, Bert Gunter wrote:

> (I know that you said your post may already be "out of date", but ...)


   Still reading ?xyplot/?barchart.

> But ?barchart says:
> "Formally, if groups is specified, then groups along with subscripts is
> passed to the panel function, ..."
> which, as I already told you, means you should consult ?panel.barchart . In
> particular, the example therein tells you exactly how the "groups" argument
> should be specified and how it works (you can change colors via the "col"
> argument, of course). Note, in particular, that "groups" must be your
> grouping variable, which means, in particular, that you need to reformat
> your data frame in what is currently referred to as "tidy" format (aka
> "long" format as opposed to "wide") -- one variable per column, one
> observation per row.  That is:
> Year     Value   Summary.Type
> 1991    91.24   "Med"
> 1991    92.89   "Max"
> ... etc.

   I saw this in examples and missed its application to my data. You've
cleared my confusion and now I _do_ understand the need for a separate
grouping column and reshaping to a long format. Thanks for explaining so

> As an aside, this is a good example of why you should adhere to this
> format for data analysis in R.

   I've done this with all my other data sets and have no excuse for not
doing so with this one. Mea culpa!

Best regards,


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