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Check and summarize individual weight information in a datras_raw object

Source: R/weight.R
check_weights.Rd

Inspect the length-weight information stored in the CA table of a datras_raw / DATRASraw object.

Usage

check_weights(x, max_length = NULL, max_weight = NULL, plot = TRUE)

Arguments

x

A datras_raw object.

max_length

Optional numeric value giving the maximum length in centimetres to retain for the analysis. Observations above this value are excluded.

max_weight

Optional numeric value giving the maximum individual weight in grams to retain for the analysis. Observations above this value are excluded.

plot

Logical. If TRUE (default), produce diagnostic plots of the observed length-weight relationship and marginal histograms of length and weight.

Value

A list with four elements:

  • lPars: a data frame with summary statistics for observed lengths,

  • wPars: a data frame with summary statistics for observed weights,

  • parEst: a data frame with estimated length-weight parameters a and b,

  • parEmp: a data frame with lookup length-weight parameters a and b, if available.

Details

The function filters to positive individual weights, optionally excludes very large lengths or weights, summarizes the observed length and weight distributions, fits a log-log length-weight relationship, and optionally plots the observed data together with the fitted curve.

The function first calls DATRAS::checkSpectrum() and then works on the CA table of the input object.

A linear model of the form $$ \log(IndWgt) = \alpha + b \log(LngtCm) $$ is fitted to the filtered observations, and the corresponding length-weight parameters are returned as: $$ a = \exp(\alpha) $$ and $$ b $$

If available, lookup length-weight parameters are also retrieved from species_info for comparison.

See also

check_lengths()

Examples


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

res <- check_weights(dab)
#> [1] "Length statistics:"
#>   min  mean median max
#> 1   3 18.94     19  35
#> [1] "Weight statistics:"
#>   min  mean median max
#> 1   1 85.93     66 559

#> [1] "Estimated LW parameters:"
#> [1] "a = 0.014 b = 2.903"
#> [1] "Lookup LW parameters in the species_info table:"
#> [1] "a = 0.007 b = 3.119"

## Restrict to plausible values
res <- check_weights(dab, max_length = 100, max_weight = 10000)
#> [1] "Length statistics:"
#>   min  mean median max
#> 1   3 18.94     19  35
#> [1] "Weight statistics:"
#>   min  mean median max
#> 1   1 85.93     66 559
#> [1] "Estimated LW parameters:"
#> [1] "a = 0.014 b = 2.903"
#> [1] "Lookup LW parameters in the species_info table:"
#> [1] "a = 0.007 b = 3.119"