vary.n: Vary n (# observed trips)

In noaa-garfo/discaRd: Cochran bycatch estimation

Vary n (# observed trips)

Description

Function to run Cochran estimator on fixed big N with a range of observed trips This function can be used to see the relationship between observer coverage and CV of discard rate. This function samples from the observed trips and is essentially one iteration of a bootstrap.

Usage

vary.n(N, bdat)

Arguments

N	Number of total commerical trips
bdat	fishery observer data

Value

dataframe of CV values (RSE of discard rate) for range of observed trips

Examples

data(eflalo)
dm = make.obs.flag.dat(eflalo, obs_level = .1)
dmo = dm[dm$OBSFLAG==1&dm$FY==1800,] # one year of data
bspec = 'LE_KG_BSS' # European seabass (FAO code BSS)
bdat = get.bydat(dmo, aggfact = 'DOCID',load = F, bspec = bspec, catch_disp = 1) # unstratified
nall = ddply(bdat, c('YEAR'), function(x) varyn(x, N = 5000))
plot(nall[,c(3:2)], typ='l')

# do it 100 times (slowly..)
nmat = matrix(NaN, nrow = nrow(bdat), ncol = 100)
for(i in 1:100){
 nmat[,i] = vary.n(5000, bdat)[,1]
}

nq = apply(nmat, 1, quantile, probs = c(.025, .5, .975), na.rm = T)
matplot((1:nrow(bdat))/nrow(bdat)*100, t(nq), typ='l', lty = c(2,1,2), col = c(2,1,2), xlab = '% Observed trips', ylab = 'CV')

noaa-garfo/discaRd documentation built on April 17, 2025, 10:32 p.m.