Equivalent in Octave to Matlab's fittype function

Question

I have some matlab code that I want to run in Octave. There's a function that does not work for octave, which is fittype. I have been googleing to find equivalent functions in Octave but to no avail.

I will post the code of that function to clarify the issue.

function bn = createFit2(b8,bi)

% --- Plot data that was originally in data set "bi vs. b8"
b8 = b8(:);
bi = bi(:);

% --- Create fit "fit"
ok_ = isfinite(b8) & isfinite(bi);
if ~all( ok_ )
warning( 'GenerateMFile:IgnoringNansAndInfs',...
    'Ignoring NaNs and Infs in data.' );
end
ft_ = fittype('poly1');

% Fit this model using new data
cf_ = fit(b8(ok_),bi(ok_),ft_);

bn = cf_.p1;

% disp(cf_.p1)

Answer 1

This is part of the Curve Fitting Toolbox and I doubt you will find an equivalent for Octave. However, because you are trying to fit a first-order polynomial, it is rather straightforward to write the fitting by hand (you are only looking for the two polynomial coefficients), or even use the polyfit function.

Answer 2

I came up with the following code. It is not giving me the same results but, I am still trying to understand what I am doing and what the output parameters are. There's the line bn=cf_.p1 in the matlab code. I assume is the property p1 of the object cf_, of the class fitobject.

function bn = createFit2(b8,bi)
% --- Plot data that was originally in data set "bi vs. b8"
b8 = b8(:);
bi = bi(:);
% --- Create fit "fit"
ok_ = isfinite(b8) & isfinite(bi);
if ~all( ok_ )
    warning( 'GenerateMFile:IgnoringNansAndInfs',...
        'Ignoring NaNs and Infs in data.' );
end
ft_ = 1 %orden del polinomio
% Fit this model using new data
cf_ = polyfit(b8(ok_),bi(ok_),ft_);
bn = cf_(1);
cf_ %muestra el valor de cf cada vez que ejecuta la función
% disp(cf_.p1)

My research is now on figuring which of the octave output is equivalent to the p1 from the cf_ MatLab fitobject.

Trial and error method showed me that indeed cf_.1 is cf_(1) in the resulting vector from fitting function fit (Matlab) and polyfit(Octave). The other thing I figured out was the polynomial orther was 1 instead of 2, wich I wasn't aware of.

Thanks all for your advices. You put me on the right track.