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X argument.
X must be a numeric matrix. The arguments dfreq and dtype indicate the format of the matrix.
Each have two possible values, meaning that a total of four data set formats are possible with dfreq=FALSE and dtype="hist", the default, X has one row per unit captured in the
experiment. Each row is an observed capture history. It must contain only zeros and ones; the number one indicates
a capture. In this case, the number of columns in the table represents the number of capture occasions in the experiment
(noted $t$). Here is an example of a data set of this type for $t=2$:
1 1
1 1
1 0
1 0
1 0
1 0
0 1
2- If dfreq=TRUE and dtype="hist", X contains one row per capture history followed by its frequency.
In that case, X has $t$+1 columns. As for the format presented previously, the first $t$ columns of X,
identifying the capture histories, must contain only zeros and ones. The number one indicates a capture. In this format,
the example data set is represented by the following matrix:
1 1 2
1 0 4
0 1 1
3- If dfreq=FALSE and dtype="nbcap", X is simply a vector of numbers of captures. The length of the
vector is $n$, the number of captured units. In this format, the example data set looks like:
2 2 1 1 1 1 1
4- If dfreq=TRUE and dtype="nbcap", X is a 2 columns matrix. The first column contains the numbers
of captures, the second columns contains the observed frequencies. In this format, the example data is:
2 2
1 5
Only few functions have the dtype argument. Functions without dtype argument accept only a data matrix X
of the form dtype="hist". So the first two formats listed above are the most common.
Formats with dtype="nbcap" are useful for experiments with a large number of capture occasions $t$. Often, no units
will be caught a large number of times, and the data set will contain no observations for $t$ captures.
Therefore, the number of capture occasions $t$ cannot be deduced from X as it can be when dtype="hist".
So if one gives a data matrix X with dtype="nbcap", one must also provide t, the number of capture
occasions, as an additional argument.
For now, the data formats with dtype="nbcap" are not generalized to the robust design. So dtype is not an
argument of the robustd.0 function.
CAPTURES IN CONTINUOUS TIME
In some capture-recapture experiments, there is no well defined capture occasions.
Captures occur in continuous time. The data set ill comes from
such an experiment. Bohning and Schon (2005) call this type of capture-recapture
data repeated counting data. These data sets always have the format dtype="nbcap".
We can estimate abundance for data of this type using the option t=Inf with the
functions closedpCI.0 and closedpCI.0. The function
descriptive also accepts t=Inf. It modifies the y coordinate
of the exploratory heterogeneity graph.