Which method ("1", "2", "3", "4") did W2.2() use by default to obtain starting values?

[guodudou]

Hello,

I am using "drm(FailRate ~ Mpa, fct = W2.2(), data = my_data)" to fit my data, and interested in understanding the method W2.2() used to obtain the starting values.

After checking the source code, seems like 4 methods are available, but I couldn't figure out how drm() calls the four methods or which method is the default. Also, I didn't find any related information online either. Can you please help explain the process?

Thank you very much and I am looking forward to your response!