Undefined function or method in function

I have a custom function below (simplified) named "my_fun", and both y1 and Observed are 10 by 1 matrix. Why do I get the error saying "Undefined function or method "Observed"? Thanks for your support!

function z = my_fun(y1) z = sum(abs(Observed-y1).^2);

>> Observed

Observed =

   31.6064
   32.2017
   30.4732
   28.6939
   28.3150
   29.6229
   31.1920
   32.2839
   31.1575
   28.5715

>> y1

y1 =

    4.6829
    4.8186
    3.2822
    1.4864
    1.0822
    2.4412
    4.3140
    4.9787
    3.8242
    1.9120

>> my_fun Undefined function or method 'Observed'

error : my_fun (line 2) z = sum(abs(Observed-y1).^2);

Answer 1

[Roger Stafford]

Since you are not passing 'Observed' to 'my_fum' as a function argument, you must make its value known to the function as a parameter in some manner. Read:

   http://www.mathworks.com/help/optim/ug/passing-extra-parameters.html

[Fumiaki Funahashi]

Great! Thank you.

Answer 2

[John D'Errico]

Because the vector Observed does not exist inside the function workspace.

Functions have their own workspace. They cannot see arrays from the caller workspace, or from the base workspace. This is true unless the function is a nested one, when it can also see variables from the parent workspace.

This is why functions allow arguments, so you can then pass in variables as needed. You did pass in y1. Why not pass in Observed also as the second argument?