I have a non-linear first order Differential Equation and a set of data satisfying that set. The coefficients as well as the data is complex and I need to fit the parameters. Any help on how to proceed shall be highly appreciated. Thanks

I am using the non-linear greybox model for the solution to this problem but somehow I am not able to make it run. It gives me the following error:

Undefined function 'nlgreyest' for input arguments of type 'idnlgrey'.

Error in Data_analysis1 (line 38) nlgr = nlgreyest(data,nlgr);

I have a data file with 1024x300 entries. I am also attaching the analysis and function files.