mf_i.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}
{* 21mar2005}{...}
{cmd:help mata I()}
{hline}
{* index identity matrix}{...}
{* index I()}{...}
{* index design matrix}{...}

{title:Title}

{p 4 4 2}
{bf:[M-5] I() -- Identity matrix}


{title:Syntax}

{p 8 12 2}
{it:real matrix}
{cmd:I(}{it:real scalar n}{cmd:)}

{p 8 12 2}
{it:real matrix}
{cmd:I(}{it:real scalar m}{cmd:,} {it:real scalar n}{cmd:)}


{title:Description}

{p 4 4 2}
{cmd:I(}{it:n}{cmd:)} 
returns the {it:n x n} identity matrix.

{p 4 4 2}
{cmd:I(}{it:m}{cmd:,} {it:n}{cmd:)} 
returns an {it:m x n} matrix with 1s down its principal diagonal and 0s 
elsewhere.


{title:Remarks}

{p 4 4 2}
Note that {cmd:I()} must be typed in uppercase.


{title:Conformability}

    {cmd:I(}{it:n}{cmd:)}:
		{it:n}:  1 {it:x} {it:1}
	   {it:result}:  {it:n x n}

    {cmd:I(}{it:m}{cmd:,} {it:n}{cmd:)}:
		{it:m}:  1 {it:x} {it:1}
		{it:n}:  1 {it:x} {it:1}
	   {it:result}:  {it:m x n}


{title:Diagnostics}

{p 4 4 2}
{cmd:I(}{it:n}{cmd:)} aborts with error if {it:n} is less than 0 or is
missing.
{it:n} is interpreted as {cmd:trunc(}{it:n}{cmd:)}.

{p 4 4 2}
{cmd:I(}{it:m}{cmd:,} {it:n}{cmd:)} 
aborts with error if {it:m} or {it:n} are less than 0
of if they are missing.
{it:m} and {it:n} are interpreted as 
{cmd:trunc(}{it:m}{cmd:)} and 
{cmd:trunc(}{it:n}{cmd:)}.


{title:Source code}

{p 4 4 2}
{cmd:I()} is built-in.


{title:Also see}

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

{p 4 13 2}
Online:  help for 
{bf:{help m4_matrix:[M-4] matrix}}
{p_end}