# Ceate a vector of state space variable like A=[x(1), x(2), x(3),.....x(21)]

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Ismaeel on 15 Mar 2015
Edited: Ismaeel on 16 Mar 2015
Hi...
How can I create a vector of state space variables by a loop to get
[x(1), x(2), x(3),.....x(21)]
I need this vector to use it in ODE15 as state space variables vector multiplied by other matrices forming DAEs.
Thanks
Ismaeel on 16 Mar 2015
Edited: Ismaeel on 16 Mar 2015
Look at this:
It is what I am working on
I did it already but without using matrices

John D'Errico on 15 Mar 2015
Edited: John D'Errico on 15 Mar 2015
The problem is, you apparently do not appreciate the basics of MATLAB.
One does not create a vector of (symbolic) variables to use in a tool like ode15s. ode15s takes a vector of NUMERIC starting values. It then returns a predicted solution based on the equations you pose, at a given set of times.
There are no symbolic variables that you need to create or define or allocate here. Really, it is best that you start reading the basic tutorials about variables and how to call functions, etc. These are fundamental concepts in MATLAB.
Regardless, as the help for sym indicates:
A = sym('A',[M N])
This creates M-by-N vectors or matrices of symbolic scalar variables.
Ismaeel on 15 Mar 2015
Thanks John. It creates A1 A2 A3 ...Amn
I need them to be like A(1) A(2) A(3)... A(mn)
Is there any function changes Amn to A(mn)?

Giorgos Papakonstantinou on 15 Mar 2015
Hallo Ismaeel. There is no need to use loop to do that. Check the colon usage of Matlab or the linspace command
For this you just simply do i.e.:
x = 1:21;
or
x = linspace(1, 10, 21);
Ismaeel on 15 Mar 2015
Hi Giorgos
ok but I do not want to have values. I mean I need them to be variables without any values.
if you print x = 1:21; you will get a vector of values not variable.
I am looking for a function or loop so that I get a vector like
[x(1), x(2), x(3),.....x(21)]