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<H1><A NAME="SECTION001350000000000000000"> </A>
<A NAME="fit-outputs"> </A>
<BR>
Outputs
</H1>
<P>
To check any typing error or missing specification, first are displayed the
options, the required precision, the maximum number of function
evaluations and the method parameters.
<P>
The frequency of the intermediate displays are controlled by the <TT>SET/FIT
PRINT=iter</TT>.
It includes the display of the iteration number, the actual
number of function evaluations, the sum of the squares of the residuals,
the so-called reduced chi, the percentage of decrease of the reduced
chi since last iteration, and, except for the NR method,
the norm of the gradient and the dimension of the space <I>V</I><SUB>1</SUB> spanned by the
Jacobian. The reduced chi square is the
<BR><P></P>
<DIV ALIGN="CENTER">
<!-- MATH: \begin{displaymath}
{ \chi^2(a^{(k)}) \over degree~of~freedom}
\end{displaymath} -->
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WIDTH="187" HEIGHT="63"
SRC="img293.gif"
ALT="\begin{displaymath}{ \chi^2(a^{(k)}) \over degree~of~freedom} \end{displaymath}">
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<BR CLEAR="ALL">
<P></P>
In any case, this is followed by the value of the
parameters. Except for the <TT>NR</TT> method, the value of the gradient and
the singular values of the Jacobian matrix are added.
<P>
At the end, a diagnostic message telling you if the convergence was
reached or if any numerical failure occurred during the algorithm.
The different messages are:
<PRE>
--> METHOD : Convergence achieved <--
*** ERR-1-METHOD : Bad initializations ... Aborting ***
*** ERR-METHOD : Likely an error in forming the derivatives ***
*** ERR-NR : Problems in inverting matrix ***
*** WARN-2-METHOD : No convergence reached ***
*** WARN-3-METHOD : Final parameters not really satisfactory ***
*** ERR-4-METHOD : No convergence in singular value decomposition ***
*** WARN-5-METHOD : parameters only a good estimation ***
*** ERR-i-METHOD : Final parameters are not satisfactory ***
</PRE>In the last message i varies from 6 to 8 and the greater
i is, the less reliable are the final value of the
parameters. For warnings and errors numbered more than 3, it is recommended to
perform another <TT>FITting</TT> with different initial guesses.
If warning 2 is displayed, do again the <TT>FITting</TT> starting with the
last computed value of the parameters (<TT>nfeval</TT> < 0 in the
<TT>FIT/...</TT> command). If an error in the derivatives is reported,
check your user functions code.
<P>
The diagnostic will be followed by the covariance matrix if you set
<TT>iter</TT> to a negative value in <TT>SET/FIT PRINT=</TT>.
<P>
Finally, the found optimal value of the parameters with their
estimated standard deviation are listed.
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<ADDRESS>
<I>Petra Nass</I>
<BR><I>1999-06-09</I>
</ADDRESS>
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