MATLAB: Solve funcion shows empty syms variables as result

matlab 2018bsolvesymsvpasolve

Hi all!
I am spotting another error in my matlab program! My code should carry out a simple system of equations, that I have written as matrices. I've used 'syms' variable to initialize the variables that I should find, and then I've employed 'solve' function to compute the equations.
More precisely, here's the code:
clear r11 r12 r13 r21 r22 r23 r31 r32 r33 tx ty tz
syms r11 r12 r13 r21 r22 r23 r31 r32 r33 tx ty tz
R=[r11 r12 r12; r21 r22 r23; r31 r32 r33];
t=[tx; ty; tz];
eqn1= ip==R*ic+t;
eqn2= mp==R*mc+t;
eqn3= rp==R*rc+t;
eqn4= lp==R*lc+t;
sol=solve([eqn1(:); eqn2(:); eqn3(:); eqn4(:)]);
Unfortunately, the solution returns me empty variables. For example, when I type "r11" in the command window to display its value, the solution is "r11=r11". I have the same error also adding "'ReturnConditions', true" as condition of the function, or using vpasolve instead of solve, or specifying the variables with respect to solve the function (R and t).
Where i am mistaken?
Thank you very much!

Best Answer

you are asking to solve 4 equation in 12 variables but you do not specify which variables to solve for . You need to indicate four variables to solve for.
The results will be returned in the struct sol so if r11 was asked to be solved for you would examine sol.r11
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