Why am I only getting 4/24 points on my Truss analysis with Matlab?

AI Thread Summary
The user is struggling with a Truss analysis problem in Matlab, consistently receiving only 4 out of 24 points on the autograder despite verifying their equations. They mention using a modified sign convention in their calculations, which may be contributing to the issue. The provided code includes a matrix setup for the truss and a loading vector, but feedback from the autograder indicates incorrect values in the output. An edit reveals a mistake in the user's manual calculations, where two values were switched. The discussion highlights the importance of careful attention to detail in both coding and manual calculations for accurate results.
gfd43tg
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Hello, I have been working on this Truss problem and have not managed to get it right. I have checked my equations over and over and everything seems to check out, but I only get 4/24 on the autograder.

Here is my paper worked out.

ImageUploadedByPhysics Forums1405563826.908265.jpg


Here is my Code. Because I don't like the opposite sign convention from the problem statement, I just used the normal sign convention and multiplied by -1, -(A\b). Whether I keep it -(A\b) or A\b, I still get 4/24 points.
Code:
function T = trussAnalyze(Px,Pz)
A = [cosd(180),cosd(30),0,cosd(270),cosd(atand(3/4)+180),0; 
    0, cosd(210),cosd(240),0,0,0;
    0,0,cosd(60),cosd(90),0,cosd(180);
    sind(180),sind(30),0,sind(atand(3/4)+180),sind(270),0;
    0,sind(210),sind(240),0,0,0;
    0,0,sind(60),sind(90),0,sind(180)];
b =[0;Px;0;0;Pz;0];
T = -(A\b);

I run the autograder and here is an example of the feedback I get
Code:
In test case 2:
    'Pure downward loading'

*Right size and class, but wrong values (even accounting for roundoff)
Argument 1:
     0

Argument 2:
   100
EDIT: Wrote it on a paper and uploaded as PDF so that my work is easier to see.
 

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my -0.6 and 1 were switched
 
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