Global symbolic variable definition

Hi Dear Matlab users

I defined a variable in .M file and assigned a symbolic value to that variable.Then I defined a function and I want to use that variable in this function I wrote.

I tried to define that variable global but program declares it double default and when it tries to assign the symbolic equation to that variable; it can not convert sym to double. How can I solve this problem ?

Thank you

[Azzi Abdelmalek]

How did you know that program declares it double?

[Kazim]

I know it makes the variable double because gives me an error that can not convert sym to double when the program tries to assign the symbolic expression to that variable. For example;

Global a

syms x y

a=x^2*y ----> Here it says can not convert sym to double . I just want my variable a becomes global not double. I want the variable remains symbolic. How could it be achieved ?

Global syms a ----> If I write like that syntax error it says

Answer 1

[Azzi Abdelmalek]

In windows command you should declare a as a sym global

syms a
global a

[Kazim]

Thank you Mr.Azzi Abdelmalek. It works but another error it gave. Let me solve it and if I can not I could request your help ?

[mohammad m]

hi in matlab 2013 i use like this but i get error that : undefined variable's. i want to use

    syms x
    global x

in my code, Then in my function in other mfile use this variable without syms in funcyion, like this

    function a=f
     f=x 
    end

but i get error, its not possible or my code is wrong? i don't want to use syms in my function, because it reduce speed.

[Walter Roberson]

global x   %has to go before the syms
syms x

and then in your function

    function a=f
     global x
     a=x 
    end

If you are trying to avoid the syms call because of the overhead, but want to use the symbol, then you should consider passing it to your function instead of using global. global is the slowest method of accessing variables. You should consider parameterizing your functions to include the symbol that you want to work with.