Description Usage Arguments Details Value Author(s) See Also

Estimate abundance given a distance function,
detection data, site data, and area. This is called internally
by `abundEstim`

. Users should use `abundEstim`

to estimate
abundance.

1 |

`dfunc` |
An estimate distance function (see |

`detectionData` |
A data frame containing information on
detections. The minimum amount of information is the detection
distances and transect or point ID where each detection
occurred. (see |

`siteData` |
A data frame containing information on the
transects or points surveyed (see |

`area` |
Total area of inference, study area size, or unit conversion.
See |

`bySite` |
A logical scalar indicating whether to compute site-level
estimates of abundance. The default ( |

If `x`

is the data frame returned when `bySite`

= TRUE,
the following is true:

For line transects,

`sum(x$abundance)*area/(2*w*sum(x$length))`

is the estimate of abundance on the study area or the abundance estimate when`bySite`

= FALSE.-
`area*sum(x$density)/nrow(x)`

is the estimate of abundance on the study area or the abundance estimate when`bySite`

= FALSE.

If `bySite`

is FALSE, a list containing the following components:

`dfunc` |
The input distance function. |

`abundance` |
Estimated abundance in the study area (if |

`n` |
The number of detections (not individuals, unless all group sizes = 1) used in the estimate of abundance. |

`area` |
Total area of inference. Study area size |

`esw` |
Effective strip width for line-transects, effective
radius for point-transects. Both derived from |

.

`n.sites` |
Total number of transects for line-transects, total number of points for point-transects. |

`tran.len` |
Total transect length. NULL for point-transects. |

`avg.group.size` |
Average group size |

If `bySite`

is TRUE, a data frame containing site-level
estimated abundance. The data frame is an exact copy of `siteData`

with the following columns tacked onto the end:

`effDist` |
The effective sampling distance at the site. For line- transects, this is ESW at the site. For points, this is EDR. |

`pDetection` |
Average probability of detection at the site. If only site-level covariates appear in the distance function, pDetection is constant within a site. When detection-level covariates are present, pDetection is the average at the site. |

`observedCount` |
The total number of individuals detected at a site. |

`abundance` |
Estimated abundance at the site. This is the sum of inflated group sizes at the site. i.e., each group size at the site is divided by its pDetection, and then summed. |

`density` |
Estimated density at the site. This is abundance
at the site divided by the sampled area at the site. E.g., for
line transects, this is abundance divided by |

`effArea` |
The effective area sampled at the site. This could be used
as an offset in a subsequent linear model. For
line transects, this is |

Trent McDonald, WEST Inc., tmcdonald@west-inc.com

Jason Carlisle, University of Wyoming and WEST Inc, jcarlisle@west-inc.com

Aidan McDonald, WEST Inc., aidan@mcdcentral.org

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