Bhattacharya {TropFishR}

Bhattacharya's method

Description

Find relative frequencies and frequency distribution of distinct cohorts in the observed length frequency distribution by resolving it into Gaussian components.

Usage

Bhattacharya(param, n_rnorm = 1000, savePlots = FALSE)

Arguments

param

a list consisting of following parameters:

• midLengths midpoints of the length class as vector,

• catch a vector with the catch per length class or a matrix with catches per length class of subsequent years;

n_rnorm

number of observations for the function rnorm. The default is 1000.

savePlots

logical; indicating whether the analyis graphs should be recorded

Details

This method includes the identify function, which allows to choose points on a graphical device manually. To stop this process please press right mouse click on the graph, and in case you are working on a windows maschine click on "Stop". An error will be caused if the graphical device is closed manually. After you have selected the points for regression analysis you will be asked if you want to redo the selection or if you want to continue. Please enter in the Console "y" for continuation if you are satisfied with your selection and the corresponding Gaussian distribution or enter "redo" if you want to repeat the selection procedure. This function allows a maximum of 12 cohorts or seperate distributions in one sample. Please find more details in the Vignette of this package or in the FAO manual by Sparre and Venema (1998) (Section 3.4.1, p. 80).

Value

A list with the input parameters and

• regressionLines dataframe with intercept, slope, start and end points of the regression lines,

• Lmean_SD_list dataframe with the mean length (Lmean), standard deviation (SD), and seperation index (SI) for each cohort,

• bhat_results dataframe with the results of the Bhattacharya method,

• distributions list with the x and y values of selected distributions,

• cohort_plots list with analysis plots (when savePlots = TRUE).

References

Bhattacharya, C.G., 1967. A simple method of resolution of a distribution into Gaussian components, Biometrics, 23:115-135

Sparre, P., Venema, S.C., 1998. Introduction to tropical fish stock assessment. Part 1. Manual. FAO Fisheries Technical Paper, (306.1, Rev. 2). 407 p.

Examples

# The following example requires to choose certain values for the regression analyses:
# first cohort:   point  2 to  8
# second cohort:  point 12 to 17
# third cohort:   point 19 to 23
# fourth cohort:  point 26 to 30


 data(synLFQ1)
 Bhattacharya(param = synLFQ1)