Need help creating a loop

28 vues (au cours des 30 derniers jours)
shanon
shanon le 19 Oct 2011
Have to create a function with a loop that formulates pi using Leibniz's formula. It has to ask the user for a positive integer n&then calculate pi to n terms (terms being 4=1 , 4/3= 2, 4/5= 3, 4/7= 4, etc..)
Leibniz's formula says that pi= 4-4/3 +4/5 - 4/7 + 4/9 - 4/11 ....
OR
pi/4= 1 - 1/3 +1 /5 - 1/7 + 1/9 - 1/11...
so far, i thought to put:
function pi= pleibniz (n)
for i= 1:n pi/4=
but then i don't know what to do! please help!

Réponse acceptée

Daniel Shub
Daniel Shub le 19 Oct 2011
I wouldn't use a loop to do this (and I love loops).
  1. How could you make z equal the sequence 1, 3, 5, 7, ..., N?
  2. How could you make y equal to 4 times the reciprocal of z?
  3. How could you make x equal to the sum of the "odd" terms of y (i.e., 4/1, 4/5, 4/9, ...) and w equal to the sum of the "even terms of y (i.e., 4/3, 4/7, ...)?
  4. How can you make v equal to the sum of x and u equal to the sum of w?
  5. How can you make t be the difference between v and u?
  5 commentaires
shanon
shanon le 19 Oct 2011
Saw it, sorry, Wayne King, writing it out for myself, so I can see it
n= 0:13;x= ((-1).^n)./(2*n+1);
%approximate pi/4
sum(x)
x1= 4.*x;
%approximate pi
sum(x1)
I don't understand why n is 0:13 though?
@Daniel, thanks for trying to make my life more difficult.... The lab is much more complex than this, all I want is a little help on one thing. You have to go, and ask me five questions? Not what I was looking for.
Daniel Shub
Daniel Shub le 19 Oct 2011
The problem with using a loop for this question is it doesn't really teach you that much about MATLAB. In fact, I would argue that following the steps that I laid out will teach you a lot more about MATLAB than the loop solution.
If you cannot look at Steven's solution and see that it works without running it, you really haven't solved the problem and the homework is only going to get harder.

Connectez-vous pour commenter.

Plus de réponses (2)

Thomas
Thomas le 19 Oct 2011

Steven
Steven le 19 Oct 2011
clear all; clc;
eps = 50; % precision
piOn4 = 1;
for i = 1:eps
piOn4 = piOn4 + (-1)^(i)*(1/(2*i+1))
end
piOn4
  3 commentaires
Jan
Jan le 19 Oct 2011
About the useless "clear all", see: http://www.mathworks.com/matlabcentral/answers/16484-good-programming-practice#answer_22301
Daniel Shub
Daniel Shub le 19 Oct 2011
Don't overwrite i!!!!!

Connectez-vous pour commenter.

Catégories

En savoir plus sur Loops and Conditional Statements dans Help Center et File Exchange

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by