Hi! On 11 Dez., 22:48, Justin Voskuhl <[email protected]> wrote:
> Let me explain a bit about what that final parameter is being used > for. But first let me state that if you use circles to draw Venn > diagrams, then for three or more circles there are many consistent set > relationships that cannot be drawn accurately. An example of this is > three equal size sets, A, B, C, where each set overlaps each other set > by say 50%, but the intersection of A, B, C is zero. Using circles to > draw this, the overlap of A^B^C won't show up in your diagram as > zero. This is an example of a very common kind of relationship, and > one that can't be drawn perfectly accurately using circles. So what > the algorithm does for cases like this is try to come up with a layout > that is "pretty good." Where "pretty good" means "not too > misleading." > > In a nutshell, the algorithm works like this: > 1. Figure out the radius for A, B and C. > 2. Figure out how far apart the center of A has to be from the center > of B to satisfy the pair-wise constraint, and do the same for B & C, > and A & C. > 3. If distance relationships satisfy the triangle inequality, then it > lays them out in a triangle, and then try to further improve the > layout taking into account A^B^C by using an optimization technique to > try to find a layout that is the least misleading. > 4. If the distance relationships do not satisfy the triangle > inequality, then the center of C is placed at the intersection of the > edges of A and B and the stochastic hill climber is started. In these > cases an "ideal" layout is much less likely to occur. > > Does this help explain what the final parameter is used for? Yes, it does. By experiments, I already guessed some trickery might be involved. I just wondered if every user is aware of the inevitable lack of accuracy. Regards, Matthias --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google Chart API" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/google-chart-api?hl=en -~----------~----~----~----~------~----~------~--~---
