MATLAB Giving "Dot indexing is not supported for variables of this type" Error When Attempting To Use Subs Function

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Logan 2024-10-10

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https://ww2.mathworks.cn/matlabcentral/answers/2158885-matlab-giving-dot-indexing-is-not-supported-for-variables-of-this-type-error-when-attempting-to-us

评论： Voss 2024-10-10

Below is the code that I am using to answer a partial differentiation question. I am able to get all the way to the end of differentiation, but when attempting to substitute "x1,y1,z1" into the function "A" I get an error given as Dot indexing is not supported for variables of this type. Any help would be greatly appreciated. Thanks!

syms x y z t A
w = 8*y*exp(x)-log(z)
x1 = log(t^2+1)
y1 = cot(t)
z1 = exp(5*t)
Q1 = diff(w,x)
Q2 = diff(x1,1)
P1 = Q1*Q2
Q3 = diff(w,z)
Q4 = diff(z1,1)
P2 = Q3*Q4
Q5 = diff(w,y)
Q6 = diff(y1,1)
P3 = Q5*Q6
A = P1 + P2 + P3
R = vpa(subs(A,{x,y,z},{x1,y1.z1}),4)
Dot indexing is not supported for variables of this type.

Error in indexing (line 956)
                R_tilde = builtin('subsref',L_tilde,Idx);