I am trying solve the differential equation by first putting it in normal, which, if I did it correctly, should be dx/dt = a8 1/3 x - 1/3 b8, where a8 is the second derivative, and b8 is the third derivative. Here is a portion of my code:
matlabFunction( [a8 +x8/3 - b8/3; a8; b8],'vars',{t,[b8;a8;x8]},'file','DE_11')
And here are the errors I get:
Error using sym/cat>checkDimensions (line 75)
CAT arguments dimensions are not consistent.
Error in sym/cat>catMany (line 38)
[resz, ranges] = checkDimensions(sz,dim);
Error in sym/cat (line 27)
ySym = catMany(dim, strs);
Error in sym/vertcat (line 19)
ySym = cat(1,args{:});
I honestly do not know what these messages are hinting at. I was hoping someone could help me decipher these error messages, and show me where I went wrong. My intention is, after these issues have been resolved, to use ode45 to solve the differential equation.
Thank you, and I apologize for my ignorance.
EDIT: Okay, after having aimlessly tried various things, I was able to get it to "work." Here is what I changed it to:
matlabFunction([b8;a8;a8 - b8/3 - x8/3], 'vars',{t8,x8,[b8,a8]},'file','DE_11')
However, I am not really certain as to why that worked, or if its even the correct input. Could someone perhaps show me why it worked? I understand that this [b8;a8;a8 - b8/3 - x8/3] represents a column vector containing my unknown functions, but I do not exactly understand this part {t8,x8,[b8,a8]}. I know that we are defining variables, but why do we use curly brackets, and why are some enclosed in square brackets, and others are not?