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Fig. 9.4. Sketch interface.
Case studies
The technique was developed with JDK (Java Development Kit) 1.6, and
executed on a personal computer (CPU 2.67GHz Dual Core, RAM 2.0GB)
under Windows Vista (32bit). Processing time is estimated as follows. The
time for level-of-detail control is O ( n ( a+s )). Quantization and clipping is
estimated to be O ( na ), and clustering is O ( ns ). The time for the sketch
interface is O ( rq ).
y
n is the total number of polylines
y
a is the number of sampled time steps
y
s is the total number of time steps
y
r is the number of representative polylines
y
q is the number of sketched time steps
In our measurement, the average time for level-of-detail control was
177 milliseconds, and the average sketch process was 1 millisecond, where
n= 376, a= 10, s= 240, r= 249, and q= 8. This result indicates that the
technique is fast enough for the interactive visualization.
We applied this technique to Japanese weather data recorded by
AMeDAS (Automated Meteorological Data Acquisition System). We
extracted time-varying temperature data observed at 376 points around
Japan every 3 hours. We then assigned weather tags including “Clear,”
“Sunny,” “Cloudy,” “Rainy,” and “Snowy” to temperature values of each
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