## 1. Symbolic substitution - MATLAB subs

Subs

This MATLAB function returns a copy of s, replacing all occurrences of old with new, and then evaluates s.

## 2. Evaluate Symbolic Expressions Using subs - MATLAB & Simulink

When you assign a value to a symbolic variable, expressions containing the variable are not automatically evaluated. Instead, evaluate expressions by using subs ...

Evaluate expressions and functions after their variables are assigned values.

## 3. Substitute Variables in Symbolic Expressions - MATLAB & Simulink

Substitute variables with other variables, numbers, vectors, or matrices.

## 4. MATLAB: subs, eval | learnonline - UniSA

subs, eval ... Suppose you have a symbolic expression f which includes the symbol x and you wish to substitute for x another symbol c or a numerical value x0.

Variable substitution and expression evaluation: subs, eval Suppose you have a symbolic expression f which includes the symbol x and you wish to substitute for x another symbol c or a numerical value x0. Then you can use the general subs command g=subs(f,old,new) which in our cases would be g=subs(f,x,c) or g=subs(f,x,x0). Here old, new can be arrays. The result g is still a symbolic variable or symbolic constant in “Maple”. Example 1: Consider a function of the two Cartesian coordinates f(x, y) = 2xy/(x2 + y2)2 . Change to polar coordinates using x = r cos θ, y = r sin θ and then determine the value of f at an arbitrary point on the unit circle r = 1. clear all syms x y r theta f=2*x*y/(x^2+y^2)^2; F=subs(f,[x y],[r*cos(theta) r*sin(theta)]); F=simple(F) % previous answer is messy f_on_unit_circle=subs(F,r,1) which gives the output F=sin(2*theta)/r^2 f_on_unit_circle=sin(2*theta) An alternative is to use the eval command. It is of the form ans=eval(S) where S is a symbolic expression for which at least one of its symbolic variables has just been given a value. If all variables are given numerical values, the answer is a number in MATLAB, not “Maple”. Example 2: Let us compare simple MATLAB and “Maple” codes which both evaluate the expression y = (x3 + 2) sec x at x = 0.123. MATLAB code Maple code using subs Maple code using eval clear all clear all clear all x=0.123 syms x syms x y=(x^3+2)*sec(x) S=(x^3+2)*sec(x); S=(x^3+2)*sec(x); y=subs(S,x,0.123) x=0.123; y...

## 5. Substitute Elements in Symbolic Matrices - MATLAB & Simulink

To replace a particular element of a matrix with a new value while keeping all other elements unchanged, use the assignment operation. For example, M(1,1) = 2 ...

Substitute elements in symbolic matrices.

## 6. substitution of values in a symbolic function with multiple variables

30 nov 2018 · I have a function f(x,y,z) that I have to derive with respect to x, evaluate in a point p(x1,x2,x3) and then elevate that number to the ...

Hi there, I have a function f(x,y,z) that I have to derive with respect to x, evaluate in a point p(x1,x2,x3) and then elevate that number to the power of two, and I'd like to do it all in a matla...

## 7. Symbolic substitution for multiple variables - MATLAB Answers

5 dec 2016 · Hi,. I wanted some explanation on the captioned. Say my N is a 6x6 matrix with 5 symbolic variables and I want to evaluate N at one go, for 5 ...

Hi, I wanted some explanation on the captioned. Say my N is a 6x6 matrix with 5 symbolic variables and I want to evaluate N at one go, for 5 different values of the variables. How do I do that u...

## 8. How to substitute multiple array syms easily? - MATLAB Answers

12 okt 2019 · subs() can accept an array of variables as its second parameter, and another array the same size as the third parameter, and does a substitution ...

Setup: A = sym('A', 4) B = sym('B', 3) x = A*A(1:4,1)+[B(1:3,1); 0] subs(x, {A, B}, {diag([3,2,1,0]), diag([1,3,5])}) Output: A = [ A1_1, A1_2, A1_3, A1_4] [ A2_1, A2_2, A2_3, A2_4] ...

## 9. Using subs() in a function when symbolic variables defined in ...

24 sep 2022 · Find the treasures in MATLAB Central and discover how the community can help you! Start Hunting! An Error ...

Hello Everyone! I'm having some problems using the subs() function and I need your help. I defined a function to calculate a jacobian matrix using symbolic variables. For example: function myJa...

## 10. Subs Command for Multivariable Function - MATLAB Answers

7 feb 2020 · Direct link to this comment ... Dot between the e and the ^ is needed if x might be non-scalar. Dot between the ) and the *tan is needed if x and ...

syms x y g=(1/2)*e^(-2*x/3).*tan(y+1); subs(g,x,0.3); subs(g,y,-0.7);

## 11. problem with subs function - MATLAB Answers - MathWorks

30 nov 2016 · Direct link to this comment ... This is probably it. @Robert, did you read the error message? Sign in to comment.

I use this command daily and sometimes it works and sometimes i get an error. I am obviously not understanding the complexity of such a simple function I have a simple symbolic function with ...

## 12. symbolic subs vectorized form - MATLAB Answers - MathWorks

22 mei 2019 · symbolic subs vectorized form. Learn more about symbolic, substitution, vectorized Symbolic Math Toolbox.

Hi there, what does work is: syms a b vals = [4 5]; subs(a + b, [a, b], vals); This returns 9 as expected. What I'm trying to do is syms a b vals = [4 5; 6 7]; subs(a + b, [a, b], v...

## 13. speed up "subs" function or faster alternative ways for symbolic ...

5 jun 2023 · I also tried using matlabFunction, but it took longer to finish, around 0.5s! So my question is is there any way to speed up the symbolic ...

I am simulating a robotic system with symbolic dynamic matrices of the robot. When I used "subs" function to substitute the symbolic variables, it took around 0.03 seconds for 1 matrix. This is rel...