data fitting in matlab

Hello everyone! I have 3 sets of data: xdata, ydata and error_ydata. I need to fit this data according to a equation like this:

    y_fit = c1*sin((2*pi*y_data)/c2 - c3) + c4

where c are constants, and the parameters to find.

I've tried several matlab functions like fittype or lsqcurvefit but they require very close initial estimates for the 4 constants to work. The point was to find these constants whichever are the initial estimates you give.

Any idea?

Thank you in advance. My best regards