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  • NLREG is in use at hundreds of universities, laboratories, and government agencies around the world (over 20 countries). For a list of a few organizations using NLREG click here.

  • If you have categorical variables, you may want to use a Decision Tree to model your data. Check out the DTREG Decision Tree Builder.

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    Fit A Four-Parameter Logistic Function

    The following NLREG program fits a 4-parameter logistic (sigmoidal) function to model heart rate as a function of blood pressure.

    The five parameters that define the function are:
    P1 = second plateau
    P2 = range of response. Note: (P1+P2) gives the first plateau
    P3 = curvature parameter
    P4 = value at inflection point

    Here are the NLREG statements to fit this function:

    Title "Four-parameter Logistic Function (Baro4)";
    Variables BP, HR;
    Parameters p1=150, p2=200, p3=0.5, p4=75;
    Function HR = p1+(p2/(1+exp(p3*(BP-p4))));
    Plot xvar=BP, xlabel="Blood Pressure", ylabel="Heart Rate";
    [ data goes here ]

    Here is a plot generated by NLREG showing the Baro4 function fitted to a a set of values.

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