I wrote a simple piece of cvx code.

```
cvx_setpath
cvx_clear
cvx_begin
variable x(n);
variable z(n);
variable w(n);
expression s;
s=x.*yapp+z-w;
expression alk;
expression hrk;
alk = x'*A*x; %A and B are positive semidefinite matrices
hrk = s'*B*s;
minimize (1/(2*lambda)*alk+1/(2*lambda_o)*hrk-ONESn'*x)
subject to
x >=0
z >=0
w >=0
x <= 1/n
z+w==u+v*ONESn;
cvx_end
```

But unfortunately, this code produces the following error

```
Undefined function or variable 'x'.
Error in twofuncsvm (line 19)
s=x.*yapp+z-w;
```

When I change the variable name to some other thing say u, for the first time the error is about other variables like z or w and after some times again the error is about u .

What is the problem, what I’m doing wrong?

Any help is appreciated. I don’t know what to do.