![]() ![]() (The resolutions and extents of the rasters need not be the same, but the higher resolution must must be an integer multiple of the lower resolution, and the cell boundaries of both rasters must coincide with cell boundaries in the higher-resolution grid.) The weighting raster must use the same coordinate system as the primary raster, and it must use a grid that is compatible with the primary raster. When they occur in the weighting raster, they cause the result of the summary operation to be NA.Įxact_extract allows for calculation of summary statistics based on multiple raster layers, such as a population-weighted temperature. Undefined ( NA) values are ignored in all of the named summary operations when they occur in the value raster. Weighted usage is discussed in more detail below. Population standard deviation of defined (non- NA) values of raster cells that intersect the polygon, multiplied by the coverage fraction and the value of a second weighting raster.įraction of covered cells that are occupied by each distinct raster value, with coverage fractions multiplied by the value of a second weighting raster. Population variance of defined (non- NA) values of cells that intersect the polygon, weighted by the product of the coverage fraction and the value of a second weighting raster. Sum of defined (non- NA) values of raster cells that intersect the polygon, multiplied by the coverage fraction and the value of a second weighting raster. Mean value of defined (non- NA) cells that intersect the polygon, weighted by the product of the coverage fraction and the value of a second weighting raster. Three additional summary operations require the use of a second weighting raster, provided in the weights argument to exact_extract: Name The population coefficient of variation of cell values, weighted by the fraction of each cell that is covered by the polygon.įraction of covered cells that are occupied by each distinct raster value. The population standard deviation of cell values, weighted by the fraction of each cell that is covered by the polygon. The population variance of cell values, weighted by the fraction of each cell that is covered by the polygon. The number of distinct raster values in cells wholly or partially covered by the polygon. Sum of values of raster cells that intersect the polygon, with each raster value weighted by its coverage fraction. ![]() The raster value with the smallest sum of coverage fractions. Minimum value of cells that intersect the polygon, ignoring coverage fractions. ![]() Median value of cells that intersect the polygon, weighted by the fraction of the cell that is covered.Īrbitrary quantile value of cells that intersect the polygon, weighted by the fraction of the cell that is covered. Mean value of cells that intersect the polygon, weighted by the fraction of the cell that is covered. Maximum value of cells that intersect the polygon, ignoring coverage fractions. The raster value with the largest sum of coverage fractions. The following summary operations are supported: Name Named operations are specified by providing a character vector with one or more operation names to the fun parameter of exact_extract. Where applicable, a named operation will provide better performance and reduced memory usage relative to an equivalent R function. Exactextractr can summarize raster values using several named operations as well as arbitrary R functions. ![]()
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