# Show and Interpolate Two Dimensional Distribution of Residuals

### Description

This function interpolates the spatial structure of residuals of a GLM through `gam`

or `surf.ls`

and optionally provides a graph.

### Usage

1 | ```
residualssurface(model, data, x, y, gam = F, npol = 2, plotit = T, filled = F, bubble = F)
``` |

### Arguments

`model` |
Result of GLM as calculated by |

`data` |
Data set that contains the spatial coordinates of the sample units used for the original model (specified as "x" and "y"). |

`x` |
Horizontal position of the sample units. |

`y` |
Vertical position of the sample units. |

`gam` |
Interpolate the spatial structure by |

`npol` |
Degree of polynomial surface as passed to |

`plotit` |
Plot the interpolated surface (through |

`filled` |
Fill the contours by |

`bubble` |
Provide a bubble graph of the residuals: circles indicate positive residuals, whereas squares indicate negative residuals. |

### Details

The function reports the results of a GAM or least-squares trend surface analysis of the spatial distribution of residuals of a model (through `residuals`

).

Optionally, a graph is produced that can contain the trend surface, filled contours and bubble graphs in addition to the spatial location of the sample units.

### Value

The function reports the results of a GAM or least-squares trend surface analysis of the spatial distribution of residuals. Optionally, a graph is provided.

### Author(s)

Roeland Kindt (World Agroforestry Centre)

### References

Kindt, R. & Coe, R. (2005) Tree diversity analysis: A manual and software for common statistical methods for ecological and biodiversity studies.

http://www.worldagroforestry.org/output/tree-diversity-analysis

### Examples

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