Creating an array of dependent symbolic variable

8 visualizaciones (últimos 30 días)
Gekkouga
Gekkouga el 13 de Oct. de 2020
Comentada: Gekkouga el 14 de Oct. de 2020
Hi,
I need to create 'N' equations based on user input 'N' which is a natural number.
Each equation is supposed to have a variable A which is a dependent on x. This 'A' term is different for each equation. Equation1 will have A1, equation2 will have A2 and so on.
I am creating this term using the expresion below.
A = sym('A', [1 N]);
This gives me symbolic variables A1, A2, A3... AN. But the problem is these terms are just symbolic variables and not dependent on x. So if I differentiate the equation with respect to x, these terms dissappear. If I use A(x) to create the variable (like a normal dependent variable), it returns a 1x1 symbolic function instead of 1xN symbolic variables.
A(x) = sym('A', [1 N]);
The above equation creates 1xN symbolic variables but the output is of type 1x1 symbolic function. Is there a way to isolate each term from this function or is there any other way to create a dependent variable array.
Thanks
  2 comentarios
madhan ravi
madhan ravi el 13 de Oct. de 2020
What’s your application by your idea?
Gekkouga
Gekkouga el 13 de Oct. de 2020
I have 'N' sections and each section has an equation.
The equations have some common terms and different terms which depend on the boundary conditions. I am creating those equations through a loop and conditional statements which will be solved later. So, I need the variable 'A' to be an array so that I can add it to the equations while iterating through the loop.

Iniciar sesión para comentar.

Respuesta aceptada

madhan ravi
madhan ravi el 13 de Oct. de 2020
Editada: madhan ravi el 13 de Oct. de 2020
A(x) = str2sym(regexprep(char(A), '(\_?\d)+', '$0(x)'))
  3 comentarios
madhan ravi
madhan ravi el 13 de Oct. de 2020
Editada: madhan ravi el 13 de Oct. de 2020
A(x) = str2sym("A" +(1:N)+"(x)")
Wanted = formula(A)
Wanted(2)
[Too many edits in mobile is so painful ;)]
Gekkouga
Gekkouga el 14 de Oct. de 2020
Thanks. It worked.
Sorry to put you through that.

Iniciar sesión para comentar.

Más respuestas (1)

Steven Lord
Steven Lord el 13 de Oct. de 2020
syms A [1 2]
eq1 = A(1)+2*A(2) == 42
eq2 = 3*A(1)-4*A(2) == 99
S = solve(eq1, eq2)
A1 = S.A1
A2 = S.A2
subs(eq1)
  1 comentario
Gekkouga
Gekkouga el 13 de Oct. de 2020
I think you didn't get my question.
I need to create an array of dependent symbolic varaible, not just symbolic variables. Something like
A = [A1(x) A2(x) A3(x)]

Iniciar sesión para comentar.

Categorías

Más información sobre Symbolic Math Toolbox en Help Center y File Exchange.

Productos


Versión

R2020b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by