Are there standard graphic symbols, other than flowcharting's "go to" symbol and the traditional hand with the extended, pointing index finger, to denote "see" or "refer to," analogous to a "hyperlink"; if yes, what are they and what do they look like?

I am looking for some feedback on the use of interactive data maps on the web. I'm experimenting with a 'histogram key' for b/w data maps.

My concern here is that the use of quasi-continuous shading might lead to 'eye bobbing' between the data map and the histogram key.

More experimental is the use of color data maps.

In this case I'm hoping that interactivity is the path to understanding, at least for the mixing of two colors.

I would be grateful for any criticism you or your readers could offer.

I look forward to your seminar in Portland later this month.

Sincerely,

Joe Meyer

Can you share any guiding principals or "best practices" in the presentation of Key Performance Indicators to the senior executives of a corporation?

My colleagues and I greatly enjoyed your New York seminar. As you showed us your Euclid and Galileo, I wondered which came first, your interest in visual information or your rare book collection?

I am looking forward to applying your principles to our work... thank you!

Any thoughts on formating information collected about a family tree? I have stolen shamelessly the font & format of your trilogy in cataloging the different family lines, i.e., wide margins in which to stick lots of interesting notes & graphics. The genealogical community's documentation completeness standard is to list the birth date & place, death date & place and, where applicable, marriage date & place for each person in the database. There are some traditional graphical displays & numbering systems as well including the afentafel. My desire is to make the end document readable even though its full of redundant-looking facts.

This question concerns how to reduce information in 4 dimensions to a representation (or set of representations) in 2 dimensions.

For background, consider the economic duopoly situation, with two firms producing non-identical products. A standard textbook way of picturing the solution is to construct "Reaction Curves" RC1 and RC2, showing each firm #1's optimal quantity response Q1 to the other's entire range of possible quantity choices Q2, and vice versa. The Cournot-Nash solution is at the intersection of the two Reaction Curves thus constructed, where each firm's choice is a best response to the other's. (The associated prices are not pictured, but are implicitly determined by the market demand function for the two products.)

Now here's the question. Suppose the firms can vary not only quantities produced (Q1 and Q2) but also the nature of their products -- measured as V1 and V2 on some numerical scale.

Instead of the previous 2-dimensional space on Q1,Q2 axes there is now a 4-dimensional space on Q1,Q2, V1,V2 axes. In this space the previous Reaction Curves now become Reaction Surfaces: firm #1 chooses a profit-maximizing (Q1,V1) vector in response to any (Q2,V2) choice on the part of its rival, and vice versa. As before, the Cournot-Nash condition will be met at the intersection, so that the firms' choices are best responses to one another.

I believe the two Reaction Surfaces will intersect generically at a single point if all the functions are ideally well-behaved, or at any rate at a finite number of points.

But is there any way of representing this solution that would permit some intuitive glimpse of the process? I've been playing without success with linked pairs of 2-dimensional diagrams. For example one diagram on Q1,Q2 axes and the other on V1,V2 axes.

Professor Tufte,

Since you are interested in things visual, I thought I would take a shot in the dark and ask you if you have any thoughts on the art of cartooning. I wouldn't expect you to, but I wouldn't want to miss out on the off chance that you did!

(I am a cartoonist and I truly enjoyed your course in Boston this year. I did not take offence at your "chartoonist" remark, and I did note your use of the B. Kliban cartoon in the magic chapter of Visual Explanations.)

Thanks,

Danny Arsenault

This is not a question but an observation.

In the movie of Galileo's sunspot illustrations I was struck by the gap in the data. Not so much that the weather was bad on that day but that Galileo had the integrity not to fudge his results.