I am new to Mathematica. I am trying to use the Nonlinear model fit function to fit some data to a logistic equation curve: 1/(1+exp[-(a+bx)]) . I am using the function NonlinearModelFit[{{x,y1}, ... {x,yk}}, form , {a,b}, {x}] I get an error saying that the function value is not a list of real numbers with dimension (k) at the initial value of the parameters {a,b} (i..e. 1,1).
Even when I follow the Example from the online help I get the same error.
I am guessing there is some parameter in the preferences set wrong, or I am doing something else real simple wrong that I even get the error with the tutorial example. One thing that is happening is that the color of the text is changing from blue to black for the name of the data string after I define it, so that is why it is not recognizing the data I give it?