# dircor: Directional mantel correlation In dave: Functions for "Data Analysis in Vegetation Ecology"

## 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

 ```1 2 3 4 5 6 7``` ```dircor(veg, x.axis, y.axis, step,...) dircor2(veg, x.axis, y.axis, step = 5) ## Default S3 method: dircor(veg, x.axis, y.axis, step,...) ## S3 method for class 'dircor' plot(x,...) ```

## 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. See also `mantel` in the vegan package.

Otto Wildi

## References

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

Wildi, O. 2017. Data Analysis in Vegetation Ecology. 3rd ed. CABI, Oxfordshire, Boston.

## Examples

 ```1 2 3 4``` ```# vegetation data is taken from sveg # the x- and y-axes are stored in object ssit o.dircor<- dircor(sveg,ssit\$x.axis,ssit\$y.axis,step=40) plot(o.dircor) ```

dave documentation built on Nov. 17, 2017, 7:45 a.m.