Computes the point- or vector-wise dissimilarity between each pair of
trajectories.

mt_distmat(data, use = "sp_trajectories", save_as = "distmat",
dimensions = c("xpos", "ypos"), weights = rep(1, length(dimensions)),
pointwise = TRUE, minkowski_p = 2, na_rm = FALSE)

## Arguments

data |
a mousetrap data object created using one of the mt_import
functions (see mt_example for details). Alternatively, a trajectory
array can be provided directly (in this case `use` will be ignored). |

use |
a character string specifying which trajectory data should be
used. |

save_as |
a character string specifying where the resulting data should
be stored. |

dimensions |
a character vector specifying which trajectory variables
should be used. Can be of length 2 or 3 for two-dimensional or
three-dimensional trajectories respectively. |

weights |
numeric vector specifying the relative importance of the
variables specified in `dimensions` . Defaults to a vector of 1s
implying equal importance. Technically, each variable is rescaled so that
the standard deviation matches the corresponding value in `weights` .
To use the original variables, set `weights = NULL` . |

pointwise |
boolean specifying the way dissimilarity between the
trajectories is measured (see Details). If `TRUE` (the default),
`mt_distmat` measures the average dissimilarity and then sums the
results. If `FALSE` , `mt_distmat` measures dissimilarity once
(by treating the various points as independent dimensions). |

minkowski_p |
an integer specifying the distance metric.
`minkowski_p = 1` computes the city-block distance, ```
minkowski_p
= 2
``` (the default) computes the Euclidian distance, `minkowski_p = 3`
the cubic distance, etc. |

na_rm |
logical specifying whether trajectory points containing NAs
should be removed. Removal is done column-wise. That is, if any trajectory
has a missing value at, e.g., the 10th recorded position, the 10th position
is removed for all trajectories. This is necessary to compute distance
between trajectories. |

## Value

A mousetrap data object (see mt_example) with an additional
object added (by default called `distmat`

) containing the distance
matrix. If a trajectory array was provided directly as `data`

, only
the distance matrix will be returned.

## Details

`mt_distmat`

computes point- or vector-wise dissimilarities between
pairs of trajectories. Point-wise dissimilarity refers to computing the
distance metric defined by `minkowski_p`

for every point of the
trajectory and then summing the results. That is, if `minkowski_p = 2`

the point-wise dissimilarity between two trajectories, each defined by a set
of x and y coordinates, is calculated as `sum(sqrt((x_i-x_j)^2 + (y_i-y_j)^2))`

.
Vector-wise dissimilarity, on the other hand refers to computing the distance
metric once for the entire trajectory. That is, vector-wise dissimilarity is
computed as `sqrt(sum((x_i-x_j)^2 + (y_i-y_j)^2))`

.

## Examples