mf_quadcross.hlp

是一个经济学管理应用软件 很难找的 但是经济学学生又必须用到

{smcl}
{* 28mar2005}{...}
{cmd:help mata quadcross()}
{hline}
{* index quadcross()}{...}
{* index quadcrossdev()}{...}
{* index deviation cross product}{...}
{* index cross product}{...}
{* index product}{...}
{* index quad precision}{...}

{title:Title}

{p 4 8 2}
{bf:[M-5] quadcross() -- Quad-precision cross products}


{title:Syntax}

{p 8 12 2}
{it:real matrix}
{cmd:quadcross(}{it:X}{cmd:,}
{it:Z}{cmd:)}

{p 8 12 2}
{it:real matrix}
{cmd:quadcross(}{it:X}{cmd:,}
{it:w}{cmd:,}
{it:Z}{cmd:)}

{p 8 12 2}
{it:real matrix}
{cmd:quadcross(}{it:X}{cmd:,}
{it:xc}{cmd:,}
{it:Z}{cmd:,}
{it:zc}{cmd:)}

{p 8 12 2}
{it:real matrix}
{cmd:quadcross(}{it:X}{cmd:,}
{it:xc}{cmd:,}
{it:w}{cmd:,}
{it:Z}{cmd:,}
{it:zc}{cmd:)}


{p 8 12 2}
{it:real matrix}
{cmd:quadcrossdev(}{it:X}{cmd:,}
{it:x}{cmd:,}
{it:Z}{cmd:,}
{it:z}{cmd:)}

{p 8 12 2}
{it:real matrix}
{cmd:quadcrossdev(}{it:X}{cmd:,}
{it:x}{cmd:,}
{it:w}{cmd:,}
{it:Z}{cmd:,}
{it:z}{cmd:)}

{p 8 12 2}
{it:real matrix}
{cmd:quadcrossdev(}{it:X}{cmd:,}
{it:xc}{cmd:,}
{it:x}{cmd:,}
{it:Z}{cmd:,}
{it:zc}{cmd:,}
{it:z}{cmd:)}

{p 8 12 2}
{it:real matrix}
{cmd:quadcrossdev(}{it:X}{cmd:,}
{it:xc}{cmd:,}
{it:x}{cmd:,}
{it:w}{cmd:,}
{it:Z}{cmd:,}
{it:zc}{cmd:,}
{it:z}{cmd:)}


{p 4 8 2}
where

	             {it:X}:  {it:real matrix X}
	            {it:xc}:  {it:real scalar xc}
	             {it:x}:  {it:real rowvector x}

	             {it:w}:  {it:real vector w}

	             {it:Z}:  {it:real matrix Z}
	            {it:zc}:  {it:real scalar zc}
	             {it:z}:  {it:real rowvector z}



{title:Description}

{p 4 4 2}
{cmd:quadcross()} makes calculations of the form

		{it:X}'{it:X} 

		{it:X}'{it:Z} 

		{it:X}{cmd:'diag(}{it:w}{cmd:)}{it:X}

		{it:X}{cmd:'diag(}{it:w}{cmd:)}{it:Z}

{p 4 4 2}
This function mirrors 
{bf:{help mf_cross:[M-5] cross()}}, the difference 
being that sums are formed in quad rather than in double precision,
so 
{cmd:quadcross()} is more accurate.

{p 4 4 2}
{cmd:quadcrossdev()} makes calculations of the form 

		({it:X}:-{it:x})'({it:X}:-{it:x})
		({it:X}:-{it:x})'({it:Z}:-{it:z})
		({it:X}:-{it:x})'{cmd:diag(}{it:w})({it:X}:-{it:x})
		({it:X}:-{it:x})'{cmd:diag(}{it:w})({it:Z}:-{it:z})

{p 4 4 2}
This function mirrors 
{bf:{help mf_crossdev:[M-5] crossdev()}}, the difference 
being that sums are formed in quad rather than in double precision, 
so 
{cmd:quadcrossdev()} is more accurate.


{title:Remarks}

{p 4 4 2}
The returned result is double precision, but the sum calculations made in 
creating that double-precision result were made in quad precision.


{title:Conformability}

{p 4 4 2}
{cmd:quadcross()} has the same conformability requirements
as {cmd:cross()}; see 
{bf:{help mf_cross:[M-5] cross()}}. 

{p 4 4 2}
{cmd:quadcrossdev()} has the same conformability requirements
as {cmd:crossdev()}; see 
{bf:{help mf_crossdev:[M-5] crossdev()}}.


{title:Diagnostics}

{p 4 4 2}
See {it:Diagnostics} under help 
{bf:{help mf_cross:[M-5] cross()}} and help 
{bf:{help mf_crossdev:[M-5] crossdev()}}.


{title:Source code}

{p 4 4 2}
Functions are built-in.


{title:Also see}

{p 4 13 2}
Manual:  {hi:[M-5] quadcross()}

{p 4 13 2}
Online:  help for 
{bf:{help mf_cross:[M-5] cross()}},
{bf:{help mf_crossdev:[M-5] crossdev()}};
{bf:{help m4_utility:[M-4] utility}},
{bf:{help m4_statistical:[M-4] statistical}}
{p_end}