help fracdydx 
                                                            also see:  fracpoly
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Title

    fracdydx -- Evaluate derivatives of fractional polynomials


Syntax

        fracdydx [varname] [, options]


    options                        Description
    -------------------------------------------------------------------------
      coeffs(# [#...]|matrixname)  defines the regression coefficients to be
                                     used
      deriv(#)                     order of derivative to be calculated
      gen(newvarname)              stores the required derivative in
                                     newvarname
      powers(# [#...]|matrixname)  defines the fractional polynomial powers
                                     to be used
    -------------------------------------------------------------------------


Description

    fracdydx evaluates derivative(s) of a fractional polynomial function at
    varname (if specified) or at the xvar most recently used by fracpoly.

    If powers() and coeffs() are not specified, powers and regression
    coefficients from the most recent fit of fracpoly are used.  Otherwise,
    powers from powers() and coefficients from coeffs() are used.


Options

    coeffs(# [#...] | matrixname) defines the regression coefficients for the
        fractional polynomial model to be used.

    deriv(#) specifies the order of derivative to be calculated.  Default #
        is 1.

    gen(newvarname) puts the deriv()th derivative of the FP into newvarname.

    powers(# [#...] | matrixname) defines the fractional polynomial powers to
        be used.


Stored quantities

    fracdydx is an R-class program and saves in the following r() locations:

        r(powers)       powers for the FP representing the deriv()th derivative
        r(coeffs)       regression coefficents for the FP representing the
                        deriv()th derivative


Examples

        . fracdydx
        . fracdydx, gen(d1)
        . fracdydx x, powers(-1 2) coeffs(1.25 0.65) deriv(2)


Author

    Patrick Royston, MRC Clinical Trials Unit, London, UK.  (
    pr@ctu.mrc.ac.uk)


Also see