A fragility curvescan be fitted by the nonlinear least squares technique, based on the Gauss-Newton algorithm.

you can use least squares, maximum likelihood, or other methods for curve fitting. If you are using MATLAB, there are a lot of built-in functions and toolboxes that can do it.

dear hayet,

easyfit program is a suitable software for tracing fragility curves.

http://www.mathwave.com/easyfit-distribution-fitting.html

best regards,

Dear Pouya;

Thank you very much for your help. it is an interesting software!

You can use SPSS software to find the relation and there are many options, nonlinear regression or other options

also you can use Excel Software by adding solver and regression analysis to excel software

If you need more help or steps for using these software we can send you full details but you should give us your full problem.

Dears friends, I thank you very much for your help and advice. I really appreciate that. cordially