Try using or tightening upper and lower bounds on coefficients.

hello

please i need your help the attatched file is my data and i want to do matlab curve fittining using custom equation:

4.112-k1*exp(-[x-477/m])-k2*exp(-[x-477/d])

i got error as in the title the values in the equation based on knowledge from data itself as paramters that already know and i want to know the other coffecient of the equation .. i have tried many methods and reducing using different algorithm using command but i still get an error please help me with this

[Matt J]

Please refer to this.

Answer 1

[Bjorn Gustavsson]

For arbitrary fitting tasks I personally prefer to use weighted least-square minimization using some optimization function,

if lsqnonlin doesn't work for you you could try the file exchange contributions: fminsearchbnd, minimize. That way I have more direct control of what is done.

HTH