# shiftpoints: Calculate a shift for plotting overlapping points In mvabund: Statistical Methods for Analysing Multivariate Abundance Data

## Description

Calculate a shift to add to overlapping points in plots for better visibility

## Usage

 ```1 2``` ```shiftpoints(x, y, sh=( max(x)-min(x))/100, centered=TRUE, method=1, reg=6, na.rm=TRUE) ```

## Arguments

 `x` a data matrix or numeric vector for use in a plot. `y` a data matrix or numeric vector for use in a plot. `sh` the maximum total shift. `centered` logical, whether the shift is centered at 0, if `FALSE` the shift will be positive only. `method` numeric, can have the value 1 or 2, see Details. `reg` numeric, see Details. `na.rm` logical, indicating whether missing values should be removed.

## Details

This function is similar to `jitter` but is defines for points in a two-dimensional plot. In contrast to `jitter` only the points with ties have a shift different from 0. The method to calculate the shift is therefore not based on random numbers.
If `method=1` (default) the individual shift will be selected so that the shift range is `sh`, without regard of the number of overlapping points
`method=2` means that for up to `reg` overlapping values a fixed shift of sh/reg is used

## Value

Returns an array of shift values with the same dimension as `x`.

## Author(s)

Ulrike Naumann and David Warton <[email protected]>.

`plot.mvabund `, `plot.mvformula`, `jitter`.
 `1` ```shiftpoints( x=c(1:5, 1:10), y=c(2:6, 1:10) ) ```