showing error on hash function

hash = hash('sha256', [K; Na; Nb])

Undefined function 'hash' for input arguments of type 'char'

[Stephen23]

Please post a link to the documentation for a function named HASH that you think you are calling.

[Dyuman Joshi]

In addition to Stephen's comment, you are over-writing the function by using it at as a variable name. That is not a good coding practice. Use a different variable name.