MATLAB: How do you use the function eval

convert to numericdoubleevalmatlab functionmost hated of allnumericsinglesymbolicsymbolic conversion

how would you plug in 2 variables which both contain a 2×1 matrix?

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Do not use eval() to turn symbolic expressions into floating point numbers. Use double() if the symbolic expressions contain only constants and functions of constants; use vpa() if the symbolic expressions contain unresolved symbolic variables.

eval() applied to a symbolic variable is not a correct thing to do. Symbolic expressions are in a different programming language that is a hybrid between MATLAB and MuPAD, and if you eval() then MATLAB will attempt to resolve them as-if they are MATLAB code, which they are not. This can be important because some of the symbolic functions take different parameters or take parameters in a different order than the MATLAB function with the same name.

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MATLAB: Need help with vector and eval

First of all, you should avoid using eval as much as possible: https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval.

Secondly, what you are trying to do can be done correctly using for loop but since, but here is a simple solution using arrayfun,

syms a b c i
A = [a*i; b-i; c+i];
aa = 10;
bb = 2;
cc = 3;
dd = 4;
ii = 1:3;
vector = cell2mat(arrayfun(@(s, i_) double(subs(s, {a b c i}, {aa bb cc i_})), A, ii', 'UniformOutput', 0));

I renamed the variables because your original variables names were overwriting previous declarations.

MATLAB: Symbolic computaion of complex number and using eval function doesnot

Do not use eval() on symbolic expressions. Symbolic expressions have a different syntax and semantics then MATLAB expressions do.

You should be using subs() instead of eval()

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MATLAB: Need help with vector and eval

MATLAB: Symbolic computaion of complex number and using eval function doesnot

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