quant
qth percentile of LFD (Length Frequency Distribution)
Description
The quant function estimates the length class corresponding to the selected percentile of the annual length frequency distribution (LFD) of a time series.
Usage
quant(freq, quantile)
Arguments
freq |
data frame of the time series of the LFD, as estimated by |
quantile |
percentile value |
Details
Length at the qth percentile (Lq)
The different percentiles of a length frequency distribution (LFD) are expected to respond differently to fishing, recruitment pulses, and loss of spawning stock. It is computed from the standardised LFD that is:
where fqj,l is the number of individuals in the length class l from the haul j standardised to the km2, and Aj is the surface trawled in the haul j.
The length at the qth percentile (Lq) is computed as:
Where l is the length class corresponding to the qth percentile (0 < q < 1) for the species i, and yl,i is the value of the catch for the length class l.
The variance of the length at the 95th percentile is computed as:
Value
The function returns a data frame containing the time series of the selected percentiles and the relative variance values.
Author(s)
Walter Zupa
Examples
library(MEDITS) merge_TATB <- m.TATB(TA,TB,"ARISFOL") merge_TATC <- m.TATC(TA,TC,"ARISFOL") GSA <- unique(TA$AREA) indices <- index.ts(merge_TATB,GSA,"ARISFOL",index = "abundance", depth_range=c(500,800), sampling = "RSS",plot=FALSE) freq <- LFD(merge_TATC,indices,sex="m",LC=1,depth_range=c(500,800)) quant(freq,0.95)