{smcl}
{* 18jun2007}{...}
{cmd:help mata rpnfcn()}{right:(SJ7-4: pr0034)}
{hline}
{* index rpn function mata}{...}
{* index rpnfcn()}{...}

{title:Title}

{p2colset 5 17 19 2}{...}
{p2col :{hi:rpnfcn()} {hline 2}}A generic function evaluator based on Reverse Polish notation (RPN){p_end}
{p2colreset}{...}


{title:Syntax}

{p 8 12 2}
{it:numeric matrix} 
{cmd:rpnfcn(}{it:pointer matrix A}{cmd:)}


{title:Description}

{p 4 4 2} {cmd:mf_rpnfcn(}{it:A}{cmd:)} returns the result of
sequentially evaluating the commands given in the rows of matrix
{it:A}.

{p 4 4 2} The fundamental commands allowed in {it:A} fall in the
following categories:

{p 8 35 2}{help mf_rpnstackfcn:Stack manipulation}{space 8} Commands that
enter matrices into the stack and that copy and interchange stack elements.

{p 8 35 2}{help mf_rpnbinop:Binary operators}{space 10} The four basic
arithmetic operations: addition, subtraction, multiplication, and
division.

{p 8 35 2}{help mf_rpndist:Single-element functions}{space 2}
Distribution functions that are executed on the current top element
of the stack and replaced with the result.

{p 8 35 2}{help mf_rpnint:Numerical integration}{space 5} Functions
used for numerical integration based on Monte Carlo with stratified,
antithetic sampling.


{title:Remarks}

{p 4 4 2} Each row of {it:A} should consist of two elements: a
pointer to a function and either a pointer to an appropriate
argument matrix or a null pointer. Upon completion of evaluation of
all rows in {it:A}, only one matrix should be present in the internal
stack setup by {cmd:rpnfcn()}, which is then returned as the result
of the evaluation.

{p 4 4 2} The user must verify that matrices are
conformable, as most procedures internally use the Mata colon
operators; see {helpb m2_op_colon:[M-2] op_colon}. The lack of
checks on matrix dimensions is considered a feature, as it, for example,
allows specifying a (1 x 2) matrix as parameter vector for a function
that then uses this pair of parameter values for evaluating all
elements of an (n x m) matrix in the stack. Equally well, an (n x 2)
parameter matrix can be supplied to the same function; now with the
implication that the pair of values in each row of the parameter
matrix is applied to all elements of the corresponding row in the (n x
m) matrix in the stack.


{title:Example}

{p 4 4 2} Consider the density for the minimum of two Weibull
distributed random variables at {it:x} with the two parameter vectors
{it:theta1} and {it:theta2}. The following code defines and evaluates
the algorithm matrix corresponding to this.

{com}. mata
{txt}{hline 49} mata (type {cmd:end} to exit) {hline}
{com}: x = (NULL)
{res}
{com}: theta1 = (NULL)
{res}
{com}: theta2 = (NULL)
{res}
{com}: fweimin = (&tostack(),  &x \
>            &enter(),    NULL \
>            &enter(),    NULL \
>            &fwei(),     &theta1 \
>            &swapst(),   NULL \
>            &Swei(),     &theta2 \
>            &product(),  NULL \
>            &rotst(),    NULL \
>            &enter(),    NULL \
>            &Swei(),     &theta1 \
>            &swapst(),   NULL \
>            &fwei(),     &theta2 \
>            &product(),  NULL \
>            &add(),      NULL
>            )
{res}
{com}: x = (0, 2, 8 \
>      .7, 1, 6)
{res}
{com}: theta1 = (-2, 2)
{res}
{com}: theta2 = (0, .3)
{res}
{com}: rpnfcn(fweimin)
{res}       {txt}          1             2             3
    {c TLC}{hline 43}{c TRC}
  1 {c |}  {res}          0   .1344860648   4.74373e-08{txt}  {c |}
  2 {c |}  {res}.6423218484   .4965861523   .0000298698{txt}  {c |}
    {c BLC}{hline 43}{c BRC}

{com}: end
{txt}{hline}


{title:Source code}

{p 4 4 2}
{view rpnfcn.mata, adopath asis:rpnfcn.mata}

{title:Author}

{p 4 4 2}{browse "http://www.almen.dk/hstovring":Henrik Støvring},
Research Unit of General Practice, University of Southern Denmark.
Please email
{browse "mailto:hstovring@health.sdu.dk":hstovring@health.sdu.dk}
if you have comments or questions or observe any problems.


{title:Also see}

{psee}
Manual:  {hi:[M-0] intro}

{psee}
Online:  
{bf:{help mata:[M-0] mata}},
{bf:{help mf_rpnstackfcn}},
{bf:{help mf_rpnbinop}}, 
{bf:{help mf_rpndist}},
{bf:{help mf_rpnint}}
{p_end}