how to remove the error showing undefined function or variable

hello, i am using function block in matlab simulation .in that want to generate matrix X1 from matrix A

for j1=1:k2

for j2=1:m1

for j3=1:n1

X1(m1*(j1-1)+j2,j3)=A(j2,j3);

end

end

end

but executing code am getting error....

Undefined function or variable 'X1'. The first assignment to a local variable determines its class.

Function 'Subsystem9/Mtesting' (#53.2154.2156), line 66, column 16:

"X1"

Launch diagnostic report.

Answer 1

[David Hill]

Preallocate X1 before the loop.

X1=zeros(m1*k2,n1);

[ram kumar]

thankyou.

but in this simulation again facing on more error

Errors occurred during parsing of MATLAB function

any suggestion to remove it.