overlay_sdm | R Documentation |

Overlay specified SDM predictions that meet the percent overlap threshold requirement onto base geometry

```
overlay_sdm(base.geom, sdm, sdm.idx, overlap.perc)
```

`base.geom` |
object of class |

`sdm` |
object of class |

`sdm.idx` |
names or indices of column(s) with data to be overlaid |

`overlap.perc` |
numeric; percent overlap threshold, i.e. percentage of each base geometry polygon must overlap with SDM prediction polygons for overlaid density value to be calculated and not set as NA |

See the eSDM GUI manual for specifics about the overlay process.
This process is equivalent to areal interpolation (Goodchild and Lam 1980),
where `base.geom`

is the target, `sdm`

is the source, and the data
specified by `sdm.idx`

are spatially intensive.

Note that `overlay_sdm`

removes rows in `sdm`

that have NA values
in the first column specified in `sdm.idx`

(i.e. `sdm.idx[1]`

),
before the overlay.
Thus, for valid overlay results, all columns of `sdm`

specified in
`sdm.idx`

must either have NA values in the same rows
or contain only NAs.

Object of class `sf`

with the geometry of `base.geom`

and
the data in the `sdm.idx`

columns of `sdm`

overlaid onto that
geometry. Note that this means all columns of `sdm`

not in
`sdm.idx`

will not be in the returned object.
Because the data are considered spatially intensive, the `agr`

attribute will be set as 'constant' for all columns in the returned object

Goodchild, M.F. & Lam, N.S.-N. (1980) Areal interpolation: a variant of the traditional spatial problem. Geo-Processing, 1, 297-312.

```
pol1.geom <- sf::st_sfc(
sf::st_polygon(list(rbind(c(1,1), c(3,1), c(3,3), c(1,3), c(1,1)))),
crs = 4326
)
pol2.geom <- sf::st_sfc(
sf::st_polygon(list(rbind(c(0,0), c(2,0), c(2,2), c(0,2), c(0,0)))),
crs = 4326
)
pol2.sf <- sf::st_sf(data.frame(Dens = 0.5), geometry = pol2.geom, crs = 4326)
overlay_sdm(pol1.geom, pol2.sf, 1, 25)
# Output 'Dens' value is NA because of higher overlap.perc value
overlay_sdm(pol1.geom, pol2.sf, 1, 50)
# These examples take longer to run
overlay_sdm(sf::st_geometry(preds.1), preds.2, 1, 50)
overlay_sdm(sf::st_geometry(preds.2), preds.1, "Density", 50)
```

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