Why my simulink Matlab Function block tell my that my matrix was not defined??

Here is my simulink Matlab Function block code. Is there something wrong with my code? Cause it shows that 'y' is not defined.

function U = self_intern(u)
%#codegen

% in=imread('3.jpg','jpg');
% u=rgb2gray(in);
% u=in(:,:,1);
[a,b]=size(u);
y=zeros(2*a,2*b);
[X,Y]=meshgrid(1:b,(1:a)');
[XI,YI]=meshgrid(1:0.5:(b+0.5),(1:0.5:(a+0.5))');
y=interp2(X,Y,u,XI,YI,'nearest');
y(:,2*b)=y(:,2*b-1);
y(2*a,:)=y(2*a-1,:);
U=y;
% figure;
%

Error： </matlabcentral/answers/uploaded_files/9665/~C5T%@K%5DXAV_)X84$7%7B3VHL.jpg>

imshow(X)**

[Ryan Livingston]

Could you please paste the text of the error in the question? The image isn't showing properly.