[gov2001-l] Problem 1c

Thanks for the quick replies. R and I are still learning how to communicate to each other, and we appreciate the counseling. After looking at the worksheet, I got rid of "&& i < iter.max" in the while loops and did it the way you had it in the example with the if statements. Everything seems to be in order now. I left "tol" in the copy and paste on accident, but pretend those are zeros instead of "tol." So for future reference, when I put "x(((x+y)/2)) != 0 && i < iter.max," did it want to run it until *both *of those conditions were met? I was going for an "or" rather than an "and," so maybe that was my issue. On Feb 26, 2008, at 11:39 PM, Jenn Larson wrote: Hi Keith, First glance suggests that one place you should look is in the argument to while(). You're saying the while loop should continue so long as two conditons are met: that the midpoint of your function fx is not equal to the tolerance level you specified in the call to your function, and that i is less than the maximum number of iterations you presumably also specified elsewhere. Usually tolerance is the maximum difference between the output of subsequent iterations you will tolerate to be content with a solution. That is, if your first six iterations produce a sequence like .25, 1, .75, .79, .80, .80, ..., and if you set a tolerance of .01, you're saying that in this case you'll be content with the first five draws: .79 and .80 are sufficiently similar that something around .80 will be your solution. Hence, the point is not to run the algorithm until the midpoint of your function *equals* the tolerance level. The point is to run the algorithm until two subsequent estimates of a function's zero are within the tolerance level of eachother. Finally, check to be sure 'i' is defined: if all this takes place in a forloop iterating through different values of something you call 'i', you're fine. But the while loops do not automatically label each iteration 'i'. Hope this helps, Jenn On Wed, Feb 27, 2008 at 2:05 AM, Keith Schnakenberg < keith.schnakenberg at gmail.com> wrote: _______________________________________________ gov2001-l mailing list gov2001-l at lists.fas.harvard.edu http://lists.fas.harvard.edu/mailman/listinfo/gov2001-l _______________________________________________ gov2001-l mailing list gov2001-l at lists.fas.harvard.edu http://lists.fas.harvard.edu/mailman/listinfo/gov2001-l