Function returning matrix instead of vector

Hello,

I have made a function for use in least squares curve fitting of the form:

f=@(xf,xdata)xf(1)*(xf(4)+((xf(2)-xdata)/(xf(3)/2))).^2/(1+((xf(2)-xdata)/(xf(3)/2)).^2)

xf should have 4 parameters

When I test the function with

f(x0f,xdata)

with x0f = [1.0000, 462.7580, 1.8007, 0], and xdata a 15x1 column vector I get a 15x15 matrix as output, when I expect a 15x1 column vector. I believe the issue is that the f function has xdata squared (.^2) both in the numerator and denominator, but I don't know how to circumvent this as there is no way to isolate xdata. Any help is appreciated.

[Travis Craddock]

P.S. Entering this function into lsqcurvefit results in an error "Function value and YDATA sizes are not equal."

Answer 1

[KSSV]

Read about element by element operations.

Repalce * with .*, / with ./

f=@(xf,xdata)xf(1)*(xf(4)+((xf(2)-xdata)./(xf(3)/2))).^2./(1+((xf(2)-xdata)./(xf(3)/2)).^2) ; 

Answer 2

[Rafael Hernandez-Walls]

f=@(xf,xdata)xf(1)*(xf(4)+((xf(2)-xdata)/(xf(3)/2))).^2./(1+((xf(2)-xdata)/(xf(3)/2)).^2)