Undefined Function or Variable but the variable is in fact Defined

So clearly k is defined, but Matlab keeps telling me it is not defined. What is going on?

>> k=1

       k =

           1
  >> f_n

        f_n = 

           @(r,n)sqrt(pi/(2*k*r))*besseli(n+.5,k*r)

    >> f_n(1,1)
             Undefined function or variable 'k'.

           Error in @(r,n)sqrt(pi/(2*k*r))*besseli(n+.5,k*r)

Answer 1

[Sean de Wolski]

The function was defined before k. When the anonymous function is created, it grabs a static snapshot of the workspace and does not update. To incorporate k, just rerun the command to create the function handle.