Graphics Reference
In-Depth Information
Degree of Dependence and Outlow Ratio
he degree of dependence and the outflow ratio, which are important characteristics
in the analysis of trade areas, can be calculated using these data. We let n
ab
be the
number of inhabitants of city Athat purchasea particular item incity B. n
ab
b
n
ab
is the proportion of people who purchase the item in city B out of the total number
of people in city A who purchased the item. When city A is fixed and this propor-
tion is calculated for each city, town and village B in the prefecture, the results are
collectively referred to as the outflow ratio from city A to each of the municipalities.
In contrast, when one city B is fixed, and the proportions are calculated for each city,
town and village A in the prefecture, the results are collectively referred to as the de-
gree of dependence on city B of each of the municipalities. he behavioral tendency
of inhabitants of a particular municipality can be determined by examining the out-
flow rate of the municipality, and when the degree of dependence is examined, the
trade area of the municipality can be determined. his system can visualize the out-
flow rate with a spider plot (Fig.
.
) and the degree of dependence with a choro-
plethmap(Fig.
.
).heannual change ineachcharacteristic can alsobevisualized
(Fig.
.
). Furthermore, because the system has a function that displays/hides in-
formation (Fig.
.
) such as the locations of government o
ces, railways, stations,
roads and borders of cities, towns and villages on the map, the relationship between
the change in the trade area and these factorscan be determined. Whena position of
public o
ce is selected for the cities, towns, and villages, corresponding time series
plots for “Degree of dependence” and “Outflow ratio” are displayed (Fig.
.
).
Ajax Technology
As well as using SVG as a tool for visualization, another feature of this system is
that it is implemented in the form of a web application written in Asynchronous
JavaScript + XML (Ajax). Ajax is implemented in the form of a web application that
executes processing while transmitting and receiving XML or plain text data and
without updating an entire web page using the HTTP communication function of
JavaScript implemented in a web browser. Because HTML is output whenever a user
request is processed in a CGI-based web application, su
cient operability is still not
achieved. However, a seamless Web application that does not make a user conscious
of the server can be realized because only the minimum information required to
updatethe webpageis obtained fromthe server using Ajax, andthe HTML andSVG
descriptions can be updated through the DOM API. Because SVG consists of XML
and a text file, SVG can be treated in the same way as HTML in websites that are
constructed using Ajax technology.
Naturally, the userinterface isa webbrowser,andthe HTMLfile, whichisa frame
consisting of three files (menu.html, layercontrol.html, okayama.svg), is loaded first
from a web server. he back end of the server side is a RDBMS. A CGI script that
receives requests from clients, sends queries to the RDBMS, receives the results, and
sends the required data to the client is installed in the web server. A map and related
information regarding Okayama prefecture are contained in okayama.svg. he map
is described by polyline elements, which are grouped together as
g
elements with
