demographic: Create population grid for age-sex groups
In wpgp/peanutButter: peanutButter

Create gridded population estimates for specific age-sex groups by disaggregating population totals using gridded age-sex proportions.

1	demographic(population, group_select, regions, proportions)

`population`	raster. Gridded population estimates.
`group_select`	character vector. Vector of age-sex groups to include in the population estimate (i.e. "f0" = females less than 1 year, "f1" = females 1 to 4 years, "f5" = females 5 to 9 years, etc.; c("m0","m1","f0","f1") = children under five)
`regions`	raster. Raster of region IDs for age-sex information.
`proportions`	data.frame. Proportion of the population in each age-sex group in each region. The first column must contain region IDs that correspond to "regions". The remaining columns are named in accordance with "group_select".