mf_dsign.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}
{* 15mar2004}{...}
{cmd:help mata dsign()}
{hline}
{* index dsign()}{...}
{* index FORTRAN}{...}
{* index sign()}{...}

{title:Title}

{p 4 4 2}
{bf:[M-5] design() -- FORTRAN-like DSIGN() function}


{title:Syntax}

{p 8 12 2}
{it:real scalar}
{cmd:dsign(}{it:real scalar a}{cmd:,}
{it:real scalar b}{cmd:)}


{title:Description}

{p 4 4 2}
{cmd:dsign(}{it:a}{cmd:,} {it:b}{cmd:)} returns {it:a} with the sign of
{it:b}, defined as abs({it:a}) if {it:b}>=0 and -abs({it:a}) otherwise.

{p 4 4 2}
This function is useful when translating FORTRAN programs.

{p 4 4 2}
Note that the in-line construction

	{cmd:(}{it:b}{cmd:>=0 ? abs(}{it:a}{cmd:) : -abs(}{it:a}{cmd:))}

{p 4 4 2}
is clearer.  Also, differentiate carefully between what {cmd:dsign()} 
returns (equivalent to the above construction) and 
{cmd:signum(}{it:b}{cmd:)}*{cmd:abs(}{it:a}{cmd:)}, which is almost 
equivalent but returns 0 when {it:b} is 0 rather than 
{cmd:abs(}{it:a}{cmd:)}.  (Message:  {cmd:dsign()} is not one of our 
favorite functions.)


{title:Conformability}

    {cmd:dsign(}{it:a}{cmd:,} {it:b}{cmd:)}:
		{it:a}:  1 {it:x} 1
		{it:b}:  1 {it:x} 1
	   {it:result}:  1 {it:x} 1


{title:Diagnostics}

{p 4 4 2}
{cmd:dsign(.,} {it:b}{cmd:)} returns {cmd:.} for all {it:b}.

{p 4 4 2}
{cmd:dsign(}{it:a}{cmd:, .)} returns abs({it:a}) for all {it:a}.


{title:Source code}

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


{title:Also see}

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

{p 4 13 2}
Online:  help for 
{bf:{help mf_sign:[M-5] sign()}};
{bf:{help m4_scalar:[M-4] scalar}}
{p_end}