# Convolve and fitting

I want to convolve two equation, then I want to find the parameters. But it doesn't give the answer and Takes too much time. What is the wrong with my code?

nlm = NonlinearModelFit[
data, {Convolve[
a*UnitStep[x - b]*c*Sqrt[x - b]*
Divide[Pi*Divide[Sqrt[d], Sqrt[x - b]]*
Exp[Pi*Divide[Sqrt[d], Sqrt[x - b]]],
Sinh[Pi*Divide[Sqrt[d], Sqrt[x - b]]]] +
a*d*Sum[Divide[4*Pi, n^3]*DiracDelta[x - b + d/n^2], {n, 1, 1}],
VoigtDistribution, x, y], b < Min[data[[All, 1]]],
b < Min[data[[All, 1]]]}, {{a, 10}, {b, -1}, c, d}, x];
nlm["BestFitParameters"]

• I noticed, that VoigtDistribution requieres 2 parameters but you provided none. – meneken17 Sep 24 '18 at 19:54
• What does it mean, is it X and y?could you tell me how to use Voigt distribution function correctly – Tharaka Sep 25 '18 at 0:13
• How do I enter those parameters with my code? I have around 600 experimental data. Could you please make it correct? – Tharaka Sep 25 '18 at 1:55
• You've asked 8 questions (with several of them appearing to be about the same dataset and model), few responses from you, and no accepting of any answers. Please respond to the answers and/or comments to get this issue resolved. – JimB Nov 26 '18 at 16:25

I neither know the context of your calculation nor do I know properties of the Voigt distribution so I cannt help you choose those: According to the reference and the wikipedia-article it should be VoigtDistribution[sigma,delta] where sigma is the standard-error of the underlying gauss distributionand delta is the $$\gamma$$ of the unerdlying Lorentz distribution.
As VoigtDistribution[\sigma,\delta] gives you a distribution you have to use
PDF[VoigtDistribution[sigma,delta],x]