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help for ^fordwal^                                                [STB-53: sg128]
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Ford-Walford method for von Bertalanffy growth function parameter estimation
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     ^fordwal^  msizevar [^if^ exp] [^in^ range] 
               [ ^,^ ^nog^raph graph_options ]


Description
-----------

This program estimates L_inf and K parameters of the von Bertalanffy growth 
function using mean at age data according to the procedure proposed by 
Ford(1933) and Walford (1946). This ado file draws the l_t vs. l_t+1 graph 
and provides a table with the numerical results.


Options
-------

^nograph^ suppresses the graph drawing

graph_options are any of the options allowed with ^graph, twoway^.


Remarks
-------

If the l_t-l_t+1 points do not have a slope less than unity, the 
program halts and exits with an error message.


Examples
--------

	. ^fordwal mlength^

Will display the Ford-Walford graph and a table with regression info and
the values for L_inf and K parameters of the von Bertalanffy equation.

	. ^fordwal mlength, xlab ylab^

Nice numbers for the axis added.

	. ^fordwal mlength, xlab ylab nog^

Suppresses the graphical display leaving only the table with numerical 
results.


Author
------

Isaias H. Salgado-Ugarte
Universidad Nacional Autonoma de Mexico
Facultad de Estudios Superiores Zaragoza
Biologia, Guelatao 66 Col. Ejercito de Oriente
Iztapalapa 09230, Mexico D.F., Mexico
(Fax 52-5-773-0151)
e-mail: isalgado@@servidor.unam.mx


Also see
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    STB: snp6 (STB-16); sg23 (STB-18) snp6.1 (STB-26); snp6.2 (STB-27)
         snp13 (STB-38)

On-line: ^help^ for @gullplot@, @bevholt@, @gullholt@, @nlvbgf@