Why matlab says Unrecognized function or variable 'x4'

Why matlab says Unrecognized function or variable 'x4' ?

[Mehmed Saad]

X = [x1 x2 x3 x4 x5 x6 x7 x8 x9 x10];

see in your workspace there is no variable with name x4 that's why Matlab says undefined function or variable x4

[viviana volpe]

I have defined all my variables and this is the result. Does this mean that my parameter K is equal to zero? I have done Ridge trace plot to find my K!

thanks

[Sahithi Kanumarlapudi]

In the result you did not plot any x4 right?