How to find the chi value with changing inputs

Question

Elise McGoldrick 2023-10-26

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2038711-how-to-find-the-chi-value-with-changing-inputs

回答： SAI SRUJAN 2023-10-30

I have physic project where I have to find the maximum value between a set of data points. My prof told me I have to use the chi squared function over a range of points. I have tried to create a code but I am struggling to get it to work. data is a 37x2 double matrix. I want to sum all of the values of the function by changing the value of vi and theta everytime but I keep getting error stating that my matrix must be square to be squared. Im not sure what to do, please any suggestions would be appriecated.

Vi = data(:,2);
Vo = 33.659;
theta = data(:,1);
for i = 120:0.5:130
    syms x;
    y(i) = symsum((Vi-Vo*cos(theta-i)^2)^2/0.1^2,[1,36]);
end
display(y)

3 个评论
显示 1更早的评论隐藏 1更早的评论

Dyuman Joshi 2023-10-26

编辑：Dyuman Joshi 2023-10-26

It's not clear to me what the objective is.

You are using symsum(), but there is no symbolic variable in the expression for which to sum through different values. Although you have defined "x" as a symbolic variable, but haven't used it.

Could you provide the mathematical formulation of the problem?

Walter Roberson 2023-10-26

theta is a column vector cos(theta-i) is a column vector. The ^ operation requires that the base array must be a square array. You need the .^ operator rather than the ^ operator.

This is not your only problem but it will solve the immediate problem.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

SAI SRUJAN 2023-10-30

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2038711-how-to-find-the-chi-value-with-changing-inputs#answer_1343416

在 MATLAB Online 中打开

Hi Elise McGoldrick,

I understand that you are facing an issue in using the chi squared function over a range of points.

The code is erroring out due to the incorrect use of "^" operator and improper syntax of "symsum" MATLAB function. Although you have defined "x" as a symbolic variable, but haven't used it in the symsum function. The operator "^" expects the Base matrix to be a square matrix whereas "cos(theta-i)" is a column vector.

You can follow the given example to proceed further.

Vi = data(:,2);
Vo = 33.659;
theta = data(:,1);
y = zeros(size(120:0.5:130));  % Preallocate the y vector for efficiency
for i = 1:numel(y)
    sum_squared_diff = sum((Vi - Vo*cos(theta - (120 + (i-1)*0.5)).^2).^2);
    y(i) = sum_squared_diff / (0.1^2);
end
display(y)