ab.gbounds {AIGIS}R Documentation

Calculate bounds on hypothetical fires in CA 1/8 degree gridcells

Description

Calculate the upper and lower bounds on values that could be contained inside fire perimeters of arbitrary area in every single 1/8 degree gridcell in California. Assumes the fire occupied the highest and lowest density block groups respectively, and does (at present) not enforce contiguity requirements. Also, at present this function is not generalizable beyond the CA wildfire problem, and area, units, recvar and appdam are the only arguments that can be safely changed from the default.

Usage

ab.gbounds(gridgpcobj = gridgpc, gws = gridinws, area = 200, units = "ha", 
  recvar = 1,  recvals = bgvals, recarea = rbgarea, appdam = TRUE, 
  dr = damrats, cap = TRUE, maskobj=MASK)

Arguments

gridgpcobj A list object containing gridcells in gpc form as well as indexing vectors. See help for the data object gridgpc for exact form.
gws Grid weights. A list of matrices giving zone indices and overlaps for each gridcell. For now gridinws is the appropriate companion object to gridgpc.
area An numeric area expressed in one of five units, specified by units.
units A character object indicating the units on area, one of:
    “ha”
    Hectares
    “sqkm”
    Square kilometers
    “sqmi”
    Square miles
    “acres”
    Acres
    “deg-area”
    Area expressed in lat-lon degree area
recvar An integer indicating which column of the record value matrix to use. That is, what variable is to be bounded.
recvals A matrix containing the data to be bounded, with rows corresponding to zones, and columns corresponding to different variables.
recarea A vector giving the area of each polygon corresponding to the records in recvals, in units of lat-lon degree area. Unlike for the standard areal interpolation functions built around arealw, this must be provided and cannot be set to “none”.
appdam CA Wildfire specific. A logical indicating whether or not to apply the empirically derived damage ratio.
dr CA Wildfire specific. A vector giving precalculated damage ratios by block group.
cap Logical passed to area2frac, indicating whether or not to automatically cap the answer at one, if the area called for is greater than the area of the cell.
maskobj A matrix of ones and zeros noting which gridcells should be used and which omitted

Details

This is primarily a midlevel wrapper, which loops calls to ab.gcbounds. It itself is wrapped by ab.gstats, which uses its output in assembling the final array reporting expected values, and bounds for housing structures, housing structures damaged, and total property value damaged.

Value

Returns an array with dimensions dim=nrow(MASK),ncol(MASK),2), where the value[i,j,] is a length two vector whose first entry is the lower bound estimate for the gridcell identified by MASK[i,j], and whose second entry is the upper bound estimate.

Note

If enough area within a gridcell is overlapping the border, the results will always be zero for the lower bound - thus fire sizes need to become reasonable large before the lower bound will be nonzero anywhere.

Author(s)

Benjamin P. Bryant, bryant@prgs.edu

See Also

ab.gcbounds

Examples


data(bgvals)
data(damrats)
data(gridgpc)
data(gridinws)
data(MASK)
data(rbgarea)

#find upper and lower bounds of housing value threatened by 200 ha fires in all
#gridcells.  (Will take a minute or two of calculating time.)

somebounds <- ab.gbounds(gridgpcobj = gridgpc, gws = gridinws, area = 200, 
  units = "ha", recvar = 2,  recvals = bgvals, recarea = rbgarea, 
  appdam = FALSE, dr = damrats, cap = TRUE)


[Package AIGIS version 1.0 Index]