loop iteration using alphabet and then its indexing

Hi,I'm trying to iterate loop using alphabet and then want to use that alphabet for indexing of my predefined array variables.The idea of doing this just to shorten the code instead of writing same formula 4 times for each array a,b,c, and d.I'm getting invalid indexing error.Can someone help me what I'm trying to do.I'll really appreciate your help.Also when I run this code clc,clear,etc not working even after running the code several times.I don't know why.Here is what I've written

clc;clear;close;
%define variables
syms x y z
%write all velocity vectors
a=[x*y^2,2*y*x^2,10];
b=[x^2+y^2+z^2,x*y+y*z+z^2,-3*x*z-z^2/2+4];
c=[x*y*z^2,x^2*y*z,z*x*y^2];
d=[x^2/2,y^2/2,3*z^2];
%determine rotation vectors for 'a'
%a(1) is 'u',a(2) is 'v' and a(3) is 'w'
for var='a':'d'    

 omega_x=(diff(str2sym(var)(3),y)-diff(str2sym(var)(2),z))/2;
omega_y=(diff(str2sym(var)(1),z)-diff(str2sym(var)(3),x))/2;
omega_z=(diff(str2sym(var)(2),x)-diff(str2sym(var)(1),y))/2;
%now print omega in vector form
fprintf('Omega_%s = (%s)i+(%s)j+(%s)k\n\n',var,omega_x,omega_y,omega_z)
%check for irrotationality
if omega_x==0 && omega_y==0 && omega_z==0
    disp('This flow field is irrotational')
end

 end

Answer 1

[Walter Roberson]

http://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval

vars = {a, b, c, d};
for varidx = 1 : length(vars)
   var = vars{varidx};
   omega_x=(diff(var(3),y)-diff(var(2),z))/2;
   and so on
end

[ajeet sahu]

Thank you for your help but result is not what I expected(That obtained without loop). here is the current result.

Here is the result that I expected or want.

[Walter Roberson]

vars = {a, b, c, d};
for varidx = 1 : length(vars)
   var = vars{varidx};
   eqn{varidx} = (diff(var(3),y)-diff(var(2),z))/2;
   and so on
end
[Omega_a, Omega_b, omega_c, Omega_d] = eqn{:};

[ajeet sahu]

I'm sorry but using this code everything is just wrong.I don't have value of rotational components in x,y and z direction.So how Can I print that using proper formatting?Also in the end resuls of omega is also wrong.Also How can apply 'if' condition by using this? Previous code was far better than this but something was not correct to obtain the proper result.Can you provide me the code which will display in same formatting as in image attached.

[ajeet sahu]

Got the right answer by small modification.Needed to make different array for names a,b,c, and d.Thankyou for your help.I've accepted your answer.Here is the complete code.

clc;clear;close;
%define variables
syms x y z
names=['a','b','c','d'];
%write all velocity vectors
a=[x*y^2,2*y*x^2,10];
b=[x^2+y^2+z^2,x*y+y*z+z^2,-3*x*z-z^2/2+4];
c=[x*y*z^2,x^2*y*z,z*x*y^2];
d=[x^2/2,y^2/2,3*z^2];
%determine rotation vectors for 'a'
%a(1) is 'u',a(2) is 'v' and a(3) is 'w'
vars = {a, b, c, d};
for i = 1 : length(vars)
  var=vars{i};  
  omega_x=(diff(var(3),y)-diff(var(2),z))/2;
  omega_y=(diff(var(1),z)-diff(var(3),x))/2;
  omega_z=(diff(var(2),x)-diff(var(1),y))/2;

    %now print omega in vector form
    fprintf('Omega_%s = (%s)i+(%s)j+(%s)k\n\n',names(i),omega_x,omega_y,omega_z)
    %check for irrotationality
    if omega_x==0 && omega_y==0 && omega_z==0

        disp('This flow field is irrotational')

    end

 end