R: Empirical variogram constructor method

varioGram.asreml {asreml} | R Documentation

## Empirical variogram constructor method

### Description

Function that calculates the empirical variogram from an `asreml` object.

### Usage

    ## S3 method for class 'asreml'
    varioGram(
      object,
      type = "default",
      spatial = "trend",
      formula = ~NULL,
      composite = TRUE,
      model = c("empirical"),
      metric = c("euclidean", "manhattan"),
      angle = 0,
      angle.tol = 180,
      nlag = 20,
      maxdist = 0.5,
      xlag = NA,
      lag.tol = 0.5,
      grid = TRUE,
      ...
    )

### Arguments

`object` | An object of class `asreml`.
`type` | Type of residuals, see `residuals.asreml` for more details (default = `"default"`).
`spatial` | Whether to include a nugget effect; see `residuals.asreml` for more details (default = `"trend"`).
`formula` | An optional model formula designed to extract residuals from the random component of the model rather than the residual component. This is a two-sided formula where the response is a pattern in the style required by the `pattern` argument of `coef.asreml`.
`composite` | Argument to `asr_varioGram`. To be used for data on a regular grid. If `TRUE`, the average of the variograms in quadrants (x, y) and (x, -y) is returned. Otherwise, both variograms are returned and identified as quadrants 1 and 4 (default = `TRUE`).
`model` | Argument to `asr_varioGram`. At the present, it can only be `"empirical"`.
`metric` | Argument to `asr_varioGram`. The distance between (x, y) points. Options are: `"euclidean"` or `"manhattan"` (default = `"euclidean"`).
`angle` | Argument to `asr_varioGram`. A vector of directions. Angles are measured in degrees anticlockwise from the x axis (default = `0`).
`angle.tol` | Argument to `asr_varioGram`. The angle subtended by each direction. That is, an arc `angle +/- angle.tol/2` (default = `180`, which gives an omnidirectional variogram).
`nlag` | Argument to `asr_varioGram`. The maximum number of lags (default = `20`).
`maxdist` | Argument to `asr_varioGram`. The fraction of the maximum distance to include in the calculation. The default is half the maximum distance in the data: `0.5`.
`xlag` | Argument to `asr_varioGram`. The width of the lags (default = `NA`).
`lag.tol` | Argument to `asr_varioGram`. The distance tolerance (default = `0.5`).
`grid` | Argument to `asr_varioGram`. If `FALSE`, forces polar variograms if (x, y) specifies a regular grid (default = `TRUE`).
`...` | Additional arguments.

### Details

Calls `asr_varioGram` to calculate the empirical semi-variogram.

### Value

A data frame including the following components:

- `x`: The original x coordinates.

- `y`: The original y coordinates.

- `gamma`: The variogram estimate.

- `distance`: The average distance for pairs in the lag.

- `np`: The number of pairs in the lag.

- `angle`: Direction, if not a regular grid.

### Examples

    ## Not run:
    data(barley)
    shf.vsr <- asreml(yield ~ Variety, residual = ~ ar1(Row):ar1(Column),
                      data = shf)
    variogram(shf.vsr)

    ## End(Not run)

[Package asreml version 4.2.0.480 Index]