Description Usage Arguments Details Value Author(s) References See Also Examples

Fits a von Bertalanffy growth curve to length and age for two or more groups.

1 2 3 |

`len` |
the vector of lengths of individual fish. |

`age` |
the vector of ages associated with the length vector. |

`group` |
the vector of character names specifying group association. The first character in the name must be a letter. |

`fixed` |
arguments specifying that Linf, K or t0 should be fitted as a constant
between groups or as separate parameters for each group. 1 = single parameter between
groups, 2 = separate parameters for each group. The order of |

`error` |
the error variance assumption. 1= constant variance for all |

`select` |
the selection of starting values of |

`Linf` |
if |

`K` |
if |

`t0` |
if |

`plot` |
logical argument specifying whether observed versus predicted and residuals graphs should be plotted. Default is FALSE. |

`control` |
see function |

A single von Bertalanffy model is fitted to the length and age data of two or more groups using function *nls* (nonlinear least squares). Parameters can be estimated for each group or as constants across groups. Individual observations of lengths-at-age are required. If error variance assumptions 2 or 3, mean lengths and required statistics are calculated. The parameters are fitted using a model.matrix where the 1st column is a row of 1s representing the parameter estimate of the reference group (group with lowest alpha-numeric order) and the remaining group columns have 1 if group identifier is the current group and 0 otherwise. See function *model.matrix*.
This is a companion function to function *vblrt*.

When seperate parameters are estimated for each group, estimates for the the non-reference groups would be the reference-group estimated parameters (e.g., Linf1 or K1 or t01) plus the coefficent estimate for the nth group (e.g., group 2: Linf2 or K2, or t02) based on the alpha-numeric order. If the parameter is assumed constant across groups, then estimates of Linf1 or K1 or t01 is used as the parameter for each group.

`results` |
list element containing summary statistics of |

`residuals` |
list element with the residuals from the model. |

Gary A. Nelson, Massachusetts Division of Marine Fisheries [email protected]

Everhart, W. H., A. W. Eipper, and W. D. Youngs. 1975. Principles of Fishery Science. Cornell University Press.

Kimura, D. K. 1980. Likelihood methods for the von Bertalanffy growth curve. U. S. Fish. Bull. 77(4): 765-776.

1 2 3 4 |

Embedding an R snippet on your website

Add the following code to your website.

For more information on customizing the embed code, read Embedding Snippets.