Confused about function syntax. Need to create my own function.

Question

Ethan Maxey 2022-2-20

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1654490-confused-about-function-syntax-need-to-create-my-own-function

评论： Image Analyst 2022-2-21

My task is as follows: Write a script that determines if the set of three vectors {v1, v2, v3} is linearly independent. If so, it prints “linearly independent” on the screen. Otherwise, it computes and prints on the screen weights c1, c2 such that v3 = c1v1 + c2v2:

This is what I've got so far. The trouble is in the Else condition. I'm unsure how to solve for c1 or c2 giving the vector equation above.

A = [3,0,6;-1,1,-3.5;4,5,0.5];
[~,p] = rref(A);
if setdiff(1:size(A,2),p) == 0
    disp('linearly independent')
else
    %prints on the screen weights c1, c2 such that v3 = c1v1 + c2v2:
    function [c1,c2] = myFun(v1,v2,v3)
    v1 = A(:, 1);
    v2 = A(:, 2);
    v3 = A(:, 3);
    c1=(v3-c2v2)/(v1);
    c2=(v3-c1v1)/(v2);
end

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Image Analyst 2022-2-20

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1654490-confused-about-function-syntax-need-to-create-my-own-function#answer_900665

在 MATLAB Online 中打开

You need to define the function AFTER your script, not within an "else" block.

A = [3,0,6;-1,1,-3.5;4,5,0.5];
% Call the function with this A:
[c1,c2] = myFun(A)
% Rest of code follows... (I didn't check it).
[~,p] = rref(A);
if setdiff(1:size(A,2),p) == 0
    disp('linearly independent')
else
    %prints on the screen weights c1, c2 such that v3 = c1v1 + c2v2:
end
% Now call the function [c1, c2] = myFun(A) somewhere above in that code.
%========================================================================
function [c1, c2] = myFun(A)
v1 = A(:, 1);
v2 = A(:, 2);
v3 = A(:, 3);
c1 = (v3 - c2v2) / v1;
c2 = (v3 - c1v1) / v2;
end

4 个评论
显示 2更早的评论隐藏 2更早的评论

Ethan Maxey 2022-2-21

在 MATLAB Online 中打开

What my code does is in the original question,

I am trying to solve for c1 and c2, given v3 = c1v2 + c2v2

function [c1, c2] = myFun(A)
v1 = A(:, 1);
v2 = A(:, 2);
v3 = A(:, 3);
c1 = (v3 - c2v2) / v1;
c2 = (v3 - c1v1) / v2;
end

Image Analyst 2022-2-21

在 MATLAB Online 中打开

I assume you mean v3 = c1v1 + c2v2

So isn't it

c = v3 / [v1, v2]

or maybe it's

c = v3 \ [v1, v2]

Make sure those vectors are column vectors, not row vectors. I'm not sure which direction the slash is off the top of my head and my MATLAB is totally tied up now doing an hours long deep learning training.

请先登录，再进行评论。