Error with fittype and custom anonymous function - limit to number of indep vars?

So, this works:

fittype(@(a,b,x1,x2) a*x1 + b*x2, 'independent',{'x1','x2'})

And this does not:

fittype(@(a,b,c,x1,x2,x3) a*x1 + b*x2 + c*x3, 'independent',{'x1','x2','x3'})

"Expression.... is not vaild.. has non-scalar coefficients, or cannot be evaluated..."

Why?

Answer 1

[Walter Roberson]

Try specifying the 'independent' option, such as in the example in the documentation:

   g = fittype( @(a, b, c, d, x, y) a*x.^2+b*x+c*exp(...
         -(y-d).^2 ), 'independent', {'x', 'y'},...
         'dependent', 'z' );

I don't think you would need to specify 'dependent'.

Answer 2

[Charlie]

Did I not?

[Walter Roberson]

Ah, so you did.

Sorry, the documentation is not really clear on some things, and I got confused.

Try then specifying the 'coefficients' option as well. I can't really tell if that will help, but it might.