R: Predicted or Fitted Values from Spatial Logistic Regression

predict.slrm {spatstat} | R Documentation

## Predicted or Fitted Values from Spatial Logistic Regression

### Description

Given a fitted Spatial Logistic Regression model, this function computes the fitted probabilities for each pixel, or the fitted point process intensity, or the values of the linear predictor in each pixel.

### Usage

     ## S3 method for class 'slrm'
    predict(object, ..., type = "intensity",
                            newdata=NULL, window=NULL)

### Arguments

`object` | a fitted spatial logistic regression model. An object of class `"slrm"`.
`...` | Optional arguments passed to `pixellate` determining the pixel resolution for the discretisation of the point pattern.
`type` | Character string (partially) matching one of `"probabilities"`, `"intensity"` or `"link"`.
`newdata` | Optional. List containing new covariate values for the prediction. See Details.
`window` | Optional. New window in which to predict. An object of class `"owin"`.

### Details

This is a method for `predict` for spatial logistic regression models (objects of class `"slrm"`, usually obtained from the function `slrm`).

The argument `type` determines which quantity is computed. If `type="intensity"`), the value of the point process intensity is computed at each pixel. If `type="probabilities"`) the probability of the presence of a random point in each pixel is computed. If `type="link"`, the value of the linear predictor is computed at each pixel.

If `newdata = NULL` (the default), the algorithm computes fitted values of the model (based on the data that was originally used to fit the model `object`).

If `newdata` is given, the algorithm computes predicted values of the model, using the new values of the covariates provided by `newdata`. The argument `newdata` should be a list; names of entries in the list should correspond to variables appearing in the model formula of the `object`. Each list entry may be a pixel image or a single numeric value.

### Value

A pixel image (object of class `"im"`) containing the predicted values for each pixel.

### Author(s)

Adrian Baddeley Adrian.Baddeley@curtin.edu.au adrian@maths.uwa.edu.au

and Rolf Turner r.turner@auckland.ac.nz

### See Also

`slrm`

### Examples

      X <- rpoispp(42)
      fit <- slrm(X ~ x+y)
      plot(predict(fit))

      data(copper)
      X <- copper$SouthPoints
      Y <- copper$SouthLines
      Z <- distmap(Y)
      fitc <- slrm(X ~ Z)
      pc <- predict(fitc)

      Znew <- distmap(copper$Lines)[copper$SouthWindow]
      pcnew <- predict(fitc, newdata=list(Z=Znew))

[Package spatstat version 1.63-3 Index]