How do I pass an equation as a parameter to a class constructor?

6 visualizaciones (últimos 30 días)
I want to make method takes an equation as input and then differentiate it and substitute with x=0,1 in the output equation
When I try to run my code I get this error:
>> aa=f(2x+1)
??? aa=f(2x+1)
|
Error: Unexpected MATLAB expression.
Is this because the constructor doesn't accept any equation?
Here is my code:
classdef SAA
%UNTITLED5 Summary of this class goes here
% Detailed explanation goes here
properties
x
equation
end
methods
function f=SAA(e)
f.equation=e;
end
function [value_1,value_2]=differntiate(~)
dydx=diff(equation,x)
% I can't complete the problem and substitute
end
end
end
any help will be appreciated.
  1 comentario
Walter Roberson
Walter Roberson el 31 de Mayo de 2011
Was this issue solved for you by your other question, http://www.mathworks.com/matlabcentral/answers/8528-how-can-i-pass-an-equation-as-input-parameter-to-function ?
(And if so, how are you doing the differentiation if what you are handed is a function handle?)

Iniciar sesión para comentar.

Respuestas (4)

John D'Errico
John D'Errico el 31 de Mayo de 2011
What can't you complete? Is part of your problem that you spelled it incorrectly as differntiate in the classdef? Then when you spell it properly when you call it, it must fail.
Or is the problem that you don't know how to use subs?
help subs
Or is the problem that you are trying to differentiate equation, rather than f.equation?
Why did you feel the need to make x a property anyway?
  4 comentarios
John D'Errico
John D'Errico el 31 de Mayo de 2011
As Paulo says, matlab requires * when you wish to multiply. Why are you writing this as a class anyway? That is truly using a Mack truck to carry a pea to Boston. And when you write f(2*x+1), where did f come from???
Eman Ahmed Elsayed
Eman Ahmed Elsayed el 31 de Mayo de 2011
when I write
f=SAA(2)// it's works well
but when I write
f=SAA(2*x+1)
the compiler said
??? Undefined function or variable 'x'.
Please, How can I fix this problem

Iniciar sesión para comentar.


Walter Roberson
Walter Roberson el 31 de Mayo de 2011
What data type is your equation? diff() only differentiates if the data type is "symbol" from the symbolic toolbox.

Todd Flanagan
Todd Flanagan el 31 de Mayo de 2011
You wouldn't pass something like 2x + 1 to DIFF. DIFF expects a vector or matrix of coefficients. In your case something like:
>> aa=f([2 1])

Eman Ahmed Elsayed
Eman Ahmed Elsayed el 31 de Mayo de 2011
when I write f=SAA(2)// it's works well but when I write f=SAA(2*x+1) the compiler said ??? Undefined function or variable 'x'. Please, How can I fix this problem
  1 comentario
Walter Roberson
Walter Roberson el 31 de Mayo de 2011
If you are going to use diff() to differentiate then your input needs to be a sym() object created by the symbolic toolkit.

Iniciar sesión para comentar.

Productos

Community Treasure Hunt

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

Start Hunting!

Translated by