Graphics Reference
In-Depth Information
Figure
.
.
Redrawn version of a portion of Playfair's
pie-circle-line chart, comparing population
and taxes in several nations
piechart and circle graph (Playfair,
). Figure
.
shows a creative combination of
different visual forms: circles, pies and lines, redrawn from Playfair (
, Plate
).
he use of two separate vertical scales for different quantities (population and
taxes) is today considered a sin in statistical graphics (you can easily jiggle either
scale to show different things). But Playfair used this device to good effect here to
try to show taxes per capita in various nations and argue that the British were over-
taxed, compared with others. But,alas, showing simple numbersbyagraph washard
enough for Playfair - he devoted several pages of text in Playfair (
) describing
how to read and understand a line graph. he idea of calculating and graphing rates
and other indirect measurements was still to come.
In this figure, the let axis and line on each circle/pie graph shows population,
while the right axis and line shows taxes. Playfair intended that the slope of the line
connectingthetwowoulddepicttherateoftaxationdirectlytotheeye;but,ofcourse,
the slope also dependson the diameters of the circles. Playfair's graphic sins can per-
hapsbeforgiven here,because thegraphclearlyshowstheslopeofthelineforBritain
to be in the opposite direction of those for the other nations.
Asomewhatlatergraph (Playfair,
),showninFig.
.
,exemplifies thebestthat
Playfair had to offer with these graphic forms. Playfair used three parallel time series
to show the price of wheat, weekly wages and reigning ruler over a
-year span
from
to
and used this graph to argue that workers had become better off in
the most recent years.
By the end of this century (
), the utility of graphing in scientific applications
prompted a Dr Buxton in London to patent and market printed coordinate paper;
curiously, a patent for lined notepaper was not issued until
. he first known
