Why i got this error?

Unrecognized function or variable 'sqrmesh'.

Error in MainFunction (line 6)

[node,elem] = sqrmesh([-1,1,-1,1],h);

Answer 1

[Walter Roberson]

The only reference I can see on the Internet to "sqrmesh" is in a part number for an Australian bee-keeping suit.

You will need to write your own sqrmesh function, or find one that someone else has written

[Mostafa Kassoum]

I have written as "squaremesh"

[Walter Roberson]

If you coded a call to sqrmesh() but you defined squaremesh() then MATLAB will not guess that sqrmesh() should refer to squaremesh()