piFuns {unmarked} | R Documentation |
Compute the cell probabilities used in the multinomial-Poisson model multinomPois.
removalPiFun(p) doublePiFun(p)
p |
matrix of detection probabilities at each site for each observation |
These two functions are provided as examples of possible functions to calculate multinomial cell probabilities. Users may write their own functions for specific sampling designs and use them in multinomPois. See the example for a user-defined function.
For removalPiFun, a matrix of cell probabilties for each site and sampling period.
For doublePiFun, a matrix of cell probabilities for each site and observer
combination. Column one is probability observer 1 but not observer 2
detects the object, column two is probability that observer 2 but not
observer 1 detects the object, and column 3 is probability of both
detecting.
(pRem <- matrix(0.5, nrow=3, ncol=3)) # Capture probabilities removalPiFun(pRem) # Cell probs (pDouble <- matrix(0.5, 3, 2)) # Observer detection probs doublePiFun(pDouble) # Cell probs # A user-defined piFun calculating removal probs when time intervals differ. # Here 10-minute counts were divided into 2, 3, and 5 minute intervals. # This function could be supplied to unmarkedFrameMPois along with the obsToY # argument shown below. instRemPiFun <- function(p) { M <- nrow(p) J <- ncol(p) pi <- matrix(NA, M, J) p[,1] <- pi[,1] <- 1 - (1 - p[,1])^2 p[,2] <- 1 - (1 - p[,2])^3 p[,3] <- 1 - (1 - p[,3])^5 for(i in 2:J) { pi[,i] <- pi[, i - 1]/p[, i - 1] * (1 - p[, i - 1]) * p[, i] } return(pi) } instRemPiFun(pRem) # Associated obsToY matrix required by unmarkedFrameMPois o2y <- diag(3) o2y[upper.tri(o2y)] <- 1 o2y