How to code this problem?
信息
此问题已关闭。 请重新打开它进行编辑或回答。
显示 更早的评论
For example,
I got
A=[ 1 2 4 5 1 .......]
I want to calculate:
X1=(x-2)(x-4)(x-5)(x-1).....
X2=(x-1)(x-4)(x-5)(x-1)....
X3=(x-1)(x-2)(x-5)(x-1)....
And so on
So how can I code it on Matlab?
Thank you very much!
2 个评论
James Tursa
2019-5-10
What have you done so far? What specific problems are you having with your code? Are you after a symbolic result, or a numeric result for a specific value of x?
John Amitage
2019-5-10
回答（1 个）
James Tursa
2019-5-10
E.g.,
syms x
A = [1 2 4 5];
n = numel(A);
P = prod(x-A);
X = cell(n,1);
for k=1:n
X{k} = P / (x-A(k));
end
This gives a cell array
>> X{1}
ans =
(x - 2)*(x - 4)*(x - 5)
>> X{2}
ans =
(x - 1)*(x - 4)*(x - 5)
>> X{3}
ans =
(x - 1)*(x - 2)*(x - 5)
>> X{4}
ans =
(x - 1)*(x - 2)*(x - 4)
10 个评论
John Amitage
2019-5-10
James Tursa
2019-5-10
编辑：James Tursa
2019-5-10
What is the A variable you are using? What version of MATLAB are you using?
John Amitage
2019-5-10
James Tursa
2019-5-10
And A?
John Amitage
2019-5-10
James Tursa
2019-5-10
Look at your original post, you have this variable
A=[ 1 2 4 5 1 .......]
I am asking you what "A" variable you are using with the code I have given you. The code works for me as I have demonstrated.
John Amitage
2019-5-10
I copied your code but without the semicolon because the program display nothing if it's there
.png)
James Tursa
2019-5-10
编辑：James Tursa
2019-5-10
So, what is the problem? It looks like the code works for you. What does this show after you run the code:
X{1}
X{2}
X{3}
X{4}
Aren't those the polynomials you want?
John Amitage
2019-5-10
James Tursa
2019-5-10
No problem! Note that it is easy to generalize this to an arbitrary sized "A" variable by using a cell array. It would be horrendous to try and implement this with named variables X1, X2, etc.
此问题已关闭。
2019-5-10
关闭：
2021-8-20
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
