Need assistance in fitting tool

Dear community I am struggling with the curve fit tool .

I have a plot where the fit supposed to be done but it gives me error and the x-axis is not in log scale.

How can I change the x-axis to log scale in the cvtoool.

Also I am not sure if the custom equation is right .

Answer 1

[Steven Lord]

"2pi" is not a valid way to write 2π in MATLAB.

y = 2*pi

y = 6.2832

[Bayram Akpinar]

Thank you but this does not fix the problem

[Steven Lord]

What is the exact text of the error message you receive now?

[Bayram Akpinar]

'Complex value computed by model function, fitting cannot continue.

Try using or tightening upper and lower bounds on coefficients.'

This error message is givene within the Cure Fitting Tool. I also need to change the x-axis scale to a log scale. I can do that when i go to file--> print to figure. But did not succeed in getting that plot into the tool where I put my equation in.