Usage
# S3 method for mask
head(x, n=6L, ...)
# S3 method for Dsurface
head(x, n=6L, ...)
# S3 method for traps
head(x, n=6L, ...)
# S3 method for capthist
head(x, n=6L, ...)
# S3 method for mask
tail(x, n=6L, ...)
# S3 method for Dsurface
tail(x, n=6L, ...)
# S3 method for traps
tail(x, n=6L, ...)
# S3 method for capthist
tail(x, n=6L, ...)