Class Notes: Tuesday
11/19/02
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Check new material on student pages (from Class
Home Page)
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Class Lunch: Meet at McAllister's, 11:00AM, on Tuesday,
Nov. 26.
Interesting New Issue: "Aspect Ratio in Graphics"
(from Section 3.1 in text)
Main Idea: Think carefully about "aspect ratio"
Ratio between vertical and horizontal "stretches"
Example: Canadian Lynx Data, previously studied on 10/29/02
- Excel default: pretty ugly
- Result of simple twiddling: better, but "too many vertical chunks"?
- Result of more vertical stretching: made the problem worse
- Result of huge horizontal stretching: made it much better?
(but harder to look at, since leaves the screen,
may want several successive pictures)
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A possible solution: vertical shrink
Proof of "better answer": eliminate connecting lines, only plot dots
- Good aspect ratio clearly shows lines
- Bad aspect ratio misses important structure
- Worth some thought in your graphics
(Excel pays no attention to this)
Interesting discussion in text: develops a theory for "getting this right"
- Based on "banking" idea
- Study population of "slopes" of line segments making the curve
- Goal: Make "average slope" = 45 degrees
- Gives algorithm (numerical recipe) for this
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Experiment to back up choice of "45 degrees", discussed in Section 4.5
For us:
- be aware of issue
- perhaps try out a few stretches
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arrive at "sensible looking answer"
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