

    \filetitle{!userdiff}{List of user m-file functions that return user-supplied derivatives}{modellang/userdiff}

	\paragraph{Syntax}
 
 \begin{verbatim}
 !userdiff
     FUNCTION_NAME, FUNCTION_NAME,
     FUNCTION_NAME
 \end{verbatim}
 \paragraph{Description}
 
 You can use any functions or your own m-file functions (provided they
 are visible on the Matlab search path or in the current working
 directory) in model files. When computing the Taylor expansion of the
 model equations, IRIS uses symbolic/automatic differentiator for all
 elementary functions. Other functions are differentiated numerically.
 
 Instead of that, you can supply first derivatives (and also second
 derivatives in case one of a function occuring in a loss function,
 \href{modellang/min}{\texttt{min}}) for you m-file functions use in the
 model file. The function must be designed to comply with certain rules,
 see \href{modellang/Contents}{Matlab functions and user functions in
 model files}, and in addition, must be also declared in the model file
 itself under the heading \texttt{!userdiff}.
 
 \paragraph{Example}


