negloglik.yx: Negative log-likelihood for forward distance and...
In david-borchers/LT2D: Line transect estimation in two dimensions

Description Usage Arguments Details Value See Also Examples

Calculates the negative log-likelihood for forward distance, y, and perpendicular distance, x, for a given hazard and perpendicular density distribution.

1	negloglik.yx(pars, y, x, hr, ystart, pi.x, w, length.b = 2, debug = FALSE)

`pars`	c(b,logphi); hazard rate and density log-parameters in a vector (see details).
`y`	scalar or vector; forward distance observations
`x`	scale or vector; perp. distance observations
`hr`	hazard rate function
`ystart`	max forward distance at which could possibly detect animal (see details).
`pi.x`	perpendicular distance density distribution
`w`	perpendicular truncation distance.
`length.b`	length of the hazard rate parameter vector

Must to ensure the hazard function has decayed to (very close to) zero by ystart. The parameter vector, pars, must be passed in with two parameters for the hazard rate first, then two parameters for perpendicular density gradient π(x) i.e. c(b,logphi).

negative log likelihood for forward distance, y and perpendicular distance x.

simXY

ystart=4;w=1
hr=h2; b=log(c(0.75,1))
pi.x=pi.norm; logphi=c(0.5,log(0.2))
N=50 #true number of animals
#generate some observations
simDat=simXY(N=N,pi.x=pi.x,logphi=logphi,
hr=hr,b=b,w=w,ystart=ystart)
x=simDat$locs$x; y=simDat$locs$y 
pars=c(b,logphi)
negloglik.yx(y,x,pars,hr,ystart,pi.x,w)