# Directional mantel correlation

### Description

Given a two-dimensional vegetation data frame and the x- and y-coordinates of the releves (the rows in the data frame) in geographical space, mantel correlation (function `mantel`

in the vegan package) is evaluated at regular intervals of direction. Direction versus correlation is plotted including 95 percent confidence interval.

### Usage

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### Arguments

`veg` |
A data frame of vegetation releves (rows) by species (columns) |

`x.axis` |
This is the x-coordinate in geographical space |

`y.axis` |
This is the y-coordinate in geographical space |

`step` |
The step length in degrees, used to draw the above mentioned function |

`x` |
An object of class "dircor" |

`...` |
Further variables used for printing |

### Details

The method presently uses correlation as distance, as.dist((1-cor(t(sveg^2.0)))/2), as distance measure for vegetation releves.

### Value

An output list of class "dircor" with at least the following intems:

`steps` |
The explicit steps used in degrees, 0 - 180 degrees |

`mean.correlation ` |
Mantel correlation at each step |

`lower.limit` |
The lower confidence limits |

`upper.limit` |
The upper confidence limits |

### Note

Computation time is fairly long because function mantel() evaluates the confidence limits for each directional step between 0 and 180 degrees.

### Author(s)

Otto Wildi

### References

Legendre, P. & Fortin, M.-J. 1989. Spatial analysis and ecological modeling. Vegetatio 80: 107–138.

Wildi, O. 2013. Data Analysis in Vegetation Ecology. 2nd ed. Wiley-Blackwell, Chichester.

### See Also

The function mantel() in the vegan package.

### Examples

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