Can't work out what I did wrong
1 回表示 (過去 30 日間)
古いコメントを表示
I have obviously done something wrong with the f function I just dont know what. I apologise as this is most likely extreamly basic.
% compute the expressions f(x) and g(x)for x=10^-1,10^-2,...,10^-14
% which values (f(x) or g(x)is more accurate
x=[10^-(1),10^-(2),10^-(3),10^-(4),10^-(5),10^-(6),10^-(7),10^-(8),10^-(9),10^-(10),10^-(11),10^-(12),10^-(13),10^-(14)];
f=(exp(2.*x)-(exp(x).*cos(x)).^2./x.^2)
g=(exp(x).*sin(x)./x).^2
% modify program to compute relative error in the inaccurate values using
% the more accurate values as estimates of the true value. For each
% x=10^-1, 10^-2,...,10^-14, print x, computed values and relative error
error_f=(f(x)-g(x)/g(x))
2 件のコメント
DGM
2021 年 10 月 3 日
Since we're comparing f against g for some measure of accuracy, we need to know what they're supposed to be. The fact that they're vastly different means that one or both of the expressions is incorrect, but there's no way to know which.
There are a couple additional things that can't hurt:
x = 10.^-(1:14); % a simpler way to write that
f = (exp(2.*x)-(exp(x).*cos(x)).^2./x.^2)
g = (exp(x).*sin(x)./x).^2
error_f = (f-g)./g % f and g are just numeric vectors
I'm not sure that's the intended way to calculate the error, but that looks like what you were trying to do.
採用された回答
DGM
2021 年 10 月 3 日
There were some parentheses misplaced in the expression for f. That said, the error is still large, but I suppose that's intentional due to what the question is asking.
x = 10.^-(1:14); % a simpler way to write that
f = (exp(2*x) - (exp(x).*cos(x)).^2)./x.^2 % parentheses on numerator
g = (exp(x).*sin(x)./x).^2
error_f = (f-g)./g % f and g are just numeric vectors
0 件のコメント
その他の回答 (2 件)
KSSV
2021 年 10 月 3 日
Replace the line
rror_f=(f(x)-g(x)/g(x)) ;
with
rror_f=(f-g./g) ;
f and g are already evaluated with the given values of x.
When you use f(x), g(x) as f, g are arrays, you are trying to index them with x which is not correct.
0 件のコメント
参考
カテゴリ
Help Center および File Exchange で Logical についてさらに検索
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!