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

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

Answer 1

[Image Analyst]

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

[Ethan Maxey]

Thanks,

Now I'm not really sure how to compute both c1 & c2. I get a couple errors when doing this...

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
    [c1] = computeC1(A);
    disp(c1)
    [c2] = computeC2(A);
    disp(c2)
end

function [c1] = computeC1(A)
v1 = A(:, 1);
v2 = A(:, 2);
v3 = A(:, 3);
c1 = (v3 - c2*v2) / v1;
end

function [c2] = computeC2(A)
v1 = A(:, 1);
v2 = A(:, 2);
v3 = A(:, 3);

c2 = (v3 - c1*v1) / v2;
end

What do I need to do in the function blocks in order to solve for c1 & c2 properly?

[Image Analyst]

I don't know what "properly" means. I don't know what your code does. All I'm doing is showing you how and where to define a function and call it. You have to figure out the rest of your code because I have no idea what it does.

[Ethan Maxey]

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]

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.