MATLAB: Substitute all solutions of a give system of equations.

equationsMATLABmupadsubstitutesystem

I would like to substitute all the solutions of a system of equations in the original system. For example I would like to do something like this in Mupad:

eqs:=[x^2-1,y^2-1]

solutions:=solve(eqs)

and then create a matrix which contains all the couples of solutions; I tried with evalAt and subs combined with map and op but had no luck.

Any suggestions?

Best Answer

syms x y
eqs=[x^2-1,y^2-1]
sol=solve(eqs)
M=[sol.x sol.y]

Related Solutions

MATLAB: Solving Diophantine Equations in MATLAB

Use the “solve” function. Before using “solve”, assume that the variables in the Diophantine equation are integers to ensure “solve” returns integer solutions. For example, solve the linear Diophantine equation 1027*x + 712*y = 1;

For MATLAB R2015a and later:

syms x y integer                % assume ‘x’ and ‘y’ are integers

eqn = 1027*x + 712*y == 1;       % declare the equation

[xSol, ySol] = solve(eqn,[x y])  % solve for ‘x’ and ‘y’

xSol =
-165
ySol =
238

For MATLAB R2014b or before:

syms x y
assume([x y], 'integer')        % assume ‘x’ and ‘y’ are integers
eqn = 1027*x + 712*y == 1;       % declare the equation
[xSol, ySol] = solve(eqn,[x y])  % solve for ‘x’ and ‘y’
xSol =
-165
ySol =
238

For details on “solve”, see: https://www.mathworks.com/help/symbolic/solve.html

For more information on assumptions, see: https://www.mathworks.com/help/symbolic/assumptions-for-symbolic-objects.html

MATLAB: Calculating max, min, and saddle points

    syms x y
    a = ((y.*x^3)+(x.*y^3)-(1.69.*x.*y));
    eqA_partial_diff_x = diff(a,x)
    eqA_partial_diff_y = diff(a,y)
    M = solve(eqA_partial_diff_x,eqA_partial_diff_y)
    N = [M.x,M.y]
    [m,n]=size(N)
    eqA_double_partial_diff_x = diff(eqA_partial_diff_x,x)
    eqA_double_partial_diff_y = diff(eqA_partial_diff_y,y)
    eqA_double_partial_diff_y_then_x = diff(eqA_partial_diff_y,x)
        x=N(:,1)
        y=N(:,2)
            eqA_double_partial_diff_x=subs(eqA_double_partial_diff_x)
    eqA_double_partial_diff_y =subs(eqA_double_partial_diff_y)
    eqA_double_partial_diff_y_then_x=subs(eqA_double_partial_diff_y_then_x)
%Determinant part
syms x y
a = ((y.*x^3)+(x.*y^3)-(1.69.*x.*y));
eqA_fx = diff(a,x)
eqA_fy = diff(a,y)
M = solve(eqA_fx,eqA_fy)
N = [M.x,M.y]
eqA_fxx = diff(eqA_fx,x)
eqA_fyy = diff(eqA_fy,y)
eqA_fyx = diff(eqA_fy,x)
D = eqA_fxx.* eqA_fyy - eqA_fyx^2
subs(D,{x,y},{N(:,1),N(:,2)})

Remark: You don’t need loop to read the values one by one instead you can substitute all the values at once

Best Answer

Related Solutions

MATLAB: Solving Diophantine Equations in MATLAB

MATLAB: Calculating max, min, and saddle points

Related Question