st: TABLEAU graphics

["Allan Reese (Cefas)" <allan.reese@cefas.co.uk>]

Nick Cox <njcoxstata@gmail.com> for once is stumped!
Subject: Re: st: create pretty charts

On Fri, Sep 7, 2012 at 10:27 AM, Nick Cox <njcoxstata@gmail.com> wrote:
> That's a good exercise for students, to say what is wrong with those
> displays. I refer to
<http://www.tableausoftware.com/learn/gallery/product-survey-analysis>

>On the bottom panel, the dates run (equally spaced)
>2/1/08 4/1/08 6/1/08 8/1/08 10/1/08 12/1/08 2/1/09 4/1/09
>Anyone else puzzled by this?

I think this is the equivalent of the Excel pitfall that "line graphs"
connect data points in series but treat the "X" series as labels.  You
will typically see such graphs for sales figures with business days
regularly spaced and weekends and holidays just ignored. You have to use
the scatterplot gallery and connect the lines to treat the "X" series as
values. 

> 1. State identifiers running alphabetically from CA to WA; that's
helpful.

I question that.  It's helpful to list states in alpha order if the
intention is to facilitate looking up individual values, but for that
intention a table would be better.  There's no reason to expect any data
pattern to follow the alphabetic order.  Sorting the states by the Y
values (height of bar or component thereof) might add information, if
readers might be interested in where states came in order.  Sorting the
states as NE-SW might be informative.

Hovering over the bottom panel (hidden meat) reveals the lines are
quadratic fits.  Extrapolating only makes sense if the X axis is metric.
Hence this plot is nonsense and the whole page looks like made-up data.
So anyone who's impressed is doing the equivalent of looking at a page
of Lorem ipsum dolor sit amet and admiring the content not the typeface.

Allan



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