Find fit with custom equation in Matlab - matlab

Question

I'm trying to find a fit with a custom equation, but I keep getting errors and don't know why. The custom equation is really big. I'm using what I found here.
This is the code (sorry about the length of the custom equation):
myfittype = fittype('a + (b*2*y) + (c*2*x+dsqrt(6)(2*xy)) + (esqrt(3)*(2*x^2+2*y^2-1)) + (fsqrt(6)(x^2-y^2)) + (gsqrt(8)(3*x^2*y-y^3)) + (hsqrt(8)(3*x^2*y+3*y^3-2*y)) + (ipsqrt(8)(x^3+3*x*y^2-2*x)) + (jpsqrt(8)(x^3-3*xy^2)) + (ksqrt(10)*(4*x^3*y-4*xy^3)+lsqrt(10)*(8*x^3*y+8*x*y^3-6*xy)) + (msqrt(5)*(6*x^4+12*x^2*y^2+6*y^4-6*x^2-6*y^2+1)) + (nsqrt(10)(4*x^4+4*x^2*y^2-3*x^2-4*x^2*y^2-4*y^4+3*y^2)) + (osqrt(10)(x^4-6*x^2*y^2+y^4)) + (psqrt(12)(5*x^4*y-10*x^2*y^3+y^5)) + (qsqrt(12)(15*x^4*y-12*x^2*y-5*y^5+4*y^3+10*x^2*y^3)) + (rsqrt(12)(10*x^4*y+20*x^2*y^3+10*y^5-12*x^2*y-12*y^3+3*y)) + (ssqrt(12)(10*x^5+20*x^3*y^2+10*x*y^4-12*x^3-12*x*y^2+3*x)) + (tsqrt(12)(5*x^5-10*x^3*y^2-4*x^3-15*x*y^4+12*xy^2)) + (usqrt(12)*(x^5-10*x^3*y^2+5*x*y^4))',... 'independent',{'x'},'dependent',{'y'},...
'coefficients',{'a','b','c','d','e','f','g','h','ip','jp','k','l','m','n','o','p','q','r','s','t','u'})
Here is the code formatted with line breaks (...) so that you can read it:
myfittype = fittype('a + (b*2*y) + (c*2*x+d*sqrt(6)*(2*x*y)) + ...
(e*sqrt(3)*(2*x^2+2*y^2-1)) + (f*sqrt(6)*(x^2-y^2)) + ...
(g*sqrt(8)*(3*x^2*y-y^3)) + (h*sqrt(8)*(3*x^2*y+3*y^3-2*y)) + ...
(ip*sqrt(8)*(x^3+3*x*y^2-2*x)) + (jp*sqrt(8)*(x^3-3*x*y^2)) + ...
(k*sqrt(10)*(4*x^3*y-4*x*y^3)+l*sqrt(10)*(8*x^3*y+8*x*y^3-6*x*y)) + ...
(m*sqrt(5)*(6*x^4+12*x^2*y^2+6*y^4-6*x^2-6*y^2+1)) + ...
(n*sqrt(10)*(4*x^4+4*x^2*y^2-3*x^2-4*x^2*y^2-4*y^4+3*y^2)) + ...
(o*sqrt(10)*(x^4-6*x^2*y^2+y^4)) + (p*sqrt(12)*(5*x^4*y-10*x^2*y^3+y^5)) + ...
(q*sqrt(12)*(15*x^4*y-12*x^2*y-5*y^5+4*y^3+10*x^2*y^3)) + ...
(r*sqrt(12)*(10*x^4*y+20*x^2*y^3+10*y^5-12*x^2*y-12*y^3+3*y)) + ...
(s*sqrt(12)*(10*x^5+20*x^3*y^2+10*x*y^4-12*x^3-12*x*y^2+3*x)) + ...
(t*sqrt(12)*(5*x^5-10*x^3*y^2-4*x^3-15*x*y^4+12*x*y^2)) + ...
(u*sqrt(12)*(x^5-10*x^3*y^2+5*x*y^4))', ...
'independent',{'x'},'dependent',{'y'}, ...
'coefficients', ...
{'a','b','c','d','e','f','g','h','ip','jp','k','l','m','n','o','p','q','r','s','t','u'})
The error says this expression is not a valid matlab expression
Hope you can help me, thanks.

Answer 1

I run your code :
The problem of your code is that
Coefficient d does not appear in the equation expression.