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Add weight-at-length estimates to a datras_raw object

Source: R/weight.R
add_weight_at_length.Rd

Estimate catch weight from length data and add the resulting weight fields to a datras_raw / DATRASraw object.

Usage

add_weight_at_length(
  x,
  max_length = NULL,
  max_weight = NULL,
  plus_group = FALSE,
  lw_source = c("lookup", "ca"),
  lookup_as_backup = FALSE,
  verbose = TRUE
)

Arguments

x

A datras_raw object.

max_length

Optional numeric value giving the maximum length in centimetres to retain when fitting the length-weight relationship. Observations above this value are excluded.

max_weight

Optional numeric value giving the maximum individual weight in grams to retain when fitting the length-weight relationship. Observations above this value are excluded.

plus_group

Logical. If TRUE the midlength for the weight calculation of the last length bin is not using the upper limit of this length bin, which might be Inf or arbitrarily high and result in an unrealistically high weight for that length bin. Instead the lower limit plus half of the size of the second last length bin is used to define the mid length of the largest length bin.

lw_source

Character string specifying the source of length-weight parameters. One of "ca" or "lookup".

lookup_as_backup

Logical. If TRUE, lookup parameters of the length-weight relationship (a, b) in the species_info table are used. Default: FALSE.

verbose

Logical. If TRUE (default), progress messages are printed.

Value

A datras_raw object with estimated weight information added.

Details

The function derives weight-at-length either from an lookup length-weight relationship fitted to the CA table or, if lw_source = "lookup", uses length-weight parameters from the species_info table.

  • If lw_source = "lookup", a linear model of the form \(\log(IndWgt) ~ \log(LngtCm)\) is fitted to positive individual weights in the CA table. Predicted weights are then assigned to length classes defined by attr(x, "cm.breaks"), multiplied by numbers-at-length, and optionally divided by haul duration.

  • If lw_source = "lookup", weight is added using length-weight parameters from the species_info table.

See also

check_weights(), add_total_weight_by_haul()

Examples


## Add numbers at length
dab <- add_numbers_at_length(dab)

## Add fitted weight-at-length estimates
x <- add_weight_at_length(dab)

## Exclude large values when fitting the length-weight model
x <- add_weight_at_length(dab, max_length = 100, max_weight = 10000)

## Use lookup weight-at-length instead from the species_info table
x <- add_weight_at_length(dab, lw_source = "lookup")