Victor Steinbok aardvark66 at GMAIL.COM
Fri Jan 3 09:29:32 UTC 2014

A few weeks ago, there was a news item regarding mall shops and
department stores making use of heat maps to "track" customers--tracking
was a bit of a misnomer, as they are not tracking individuals but rather
look for clustering of shoppers around shelf space.

Heatmap or heat map, originally, is a thermal image or a composition of
thermal images that show different temperature or intensity by location,
usually via use of different, often suggestive colors (e.g., blue,
green, yellow, orange, red, in order of increasing temperature). This
may be a "map" of an area (e.g., a satellite IR image of a combat zone
or a spy image http://goo.gl/sSRo8H), a body or an object (e.g., thermal
images of "heat leaks" in a house http://goo.gl/NTfRoA; body temperature
to locate an infection or for other medical purposes
http://goo.gl/SQtMT; heat distribution in a frying pan; invasion-less
search of a house trying to locate marijuana being grown
http://goo.gl/Db2tV4, etc. http://goo.gl/0RK854). Note that not all
cited sites use the expression "heat map" but stick with the more
accurate "thermal image" or "thermal imaging".

This quickly evolved into a more general class of images, perhaps best
classified as "cluster maps". The mall tracking usage suggests why.

 From Wiki:
> A heat map is a graphical representation of data where the individual
> values contained in a matrix are represented as colors. Fractal maps
> and tree maps both often use a similar system of color-coding to
> represent the values taken by a variable in a hierarchy. The term is
> also used to mean its thematic application as a choropleth map. The
> term "Heatmap" was originally coined and trademarked by software
> designer Cormac Kinney in 1991, to describe a 2D display depicting
> real time financial market information.
> Heat maps originated in 2D displays of the values in a data matrix.
> Larger values were represented by small dark gray or black squares
> (pixels) and smaller values by lighter squares. Sneath (1957)
> displayed the results of a cluster analysis by permuting the rows and
> the columns of a matrix to place similar values near each other
> according to the clustering. Jacques Bertin used a similar
> representation to display data that conformed to a Guttman scale. The
> idea for joining cluster trees to the rows and columns of the data
> matrix originated with Robert Ling in 1973. Ling used overstruck
> printer characters to represent different shades of gray, one
> character-width per pixel. Leland Wilkinson developed the first
> computer program in 1994 (SYSTAT) to produce cluster heat maps with
> high-resolution color graphics. The Eisen et al. display shown in the
> figure is a replication of the earlier SYSTAT design.

There should be no surprise that this idea gets traction in marketing.

OED has no entry for heat map (any spelling) but it does show up in a

plot, v.1 4.b
> 1989 Best 14 Apr. 26/3 Thermography, in which the temperature of
> various parts of the leg is used to plot a heat map.

Today I came across the use of "heatmap" that may predate this
particular usage, but does not appear likely to predate the original use
of "heatmap". But rather than a thermal image, or image of heat
distribution, it's a map that represents "hotness". In this case it's a
map of "hot" restaurants in Manhattan (or other boroughs).

> More often than not, tipsters, readers, friends and family of Eater
> have one question: Where should I eat right now? Restaurant obsessives
> want to know what's new, what's hot, which favorite chef just launched
> a sophomore effort, what Michael White is up to these days. And while
> the Eater 38 is a crucial resource covering old standbys and
> neighborhood essentials across the city, it is not a chronicle of the
> "it" places of the moment. Thus, we offer the Eater Heatmap, which
> will change continually to always highlight where the foodie crowds
> are flocking to at the moment.
> Check out the map of Manhattan's 20 hottest restaurants below, and
> stay tuned for the Brooklyn and Queens maps later this week.

This strikes me as a low-budget, manually constructed (and fairly
one-dimensional) cluster image. There is no second variable or color
change with intensity. So it's really riffing off the idea based on
lexical connection between "heat" and "hot", not so much an extension of
the more general "heat map".


PS: Quite unrelated, looking over the plot v.1 entry mentioned above, I
realized that it's missing the Star Trek meaning of "plot"--as in "plot
the course". Of course, it's not just Star Trek. But there is a
quotation in OED that does use it.

way, n.1
1983 /Times <javascript:void(0)>/ 6 Sept. 26/2 They plot course by
typing..a series of ‘way-points’ into the computer. Such way-points
occur every four hundred miles, so even if one were wrong, the next
should put aircraft back on course.

The American Dialect Society - http://www.americandialect.org

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