MRGmerge: Merge two or more multi-resolution grids to a common...

In MRG: Create Non-Confidential Multi-Resolution Grids

Merge two or more multi-resolution grids to a common resolution

Description

Merge two or more multi-resolution grids to a common resolution

Usage

MRGmerge(himg1, himg2, vars1, vars2, na.rm = TRUE, postProcess = FALSE, ...)

Arguments

himg1	Either a grid resulting from a call to multiResGrid, or a list of such grids
himg2	A grid resulting from a call to multiResGrid
vars1	Variable(s) of interest that should be merged from the first grid, or a list of variables, one for each grid in the list himg1
vars2	Variable(s) of interest that should be merged from the second grid
na.rm	Should NA values be removed when summing values (essentially treating them equal to zero)
postProcess	Logical; should the postprocessing be done as part of creation of the multiresolution grid (TRUE), or be done in a separate step afterwards (FALSE). The second option is useful when wanting to check the confidential grid cells of the final map
...	Additional grids (himg3, himg4, ...) and variables (vars3, vars4, ...) to be merged. Additional grids and variables must be named.

Details

This function can merge different multi-resolution grids to a common resolution, i.e., it will select the grid cells with the lowest resolution, as these are the ones defining the restrictions.

The function will merge the variable names in vars1, vars2, ... if they exist. If they are missing, the function will look for variable names in the attributes of the grids (attr(himg, "vars")). These are added by multiResGrid, but will often disappear if the grid has been manipulated, or has been exported to another format for transmission.

If the variables are not given as vars or attributes, the function will try to guess them from the column names. Typical column names used by MRG (mostly temporary variables such as small, confidential etc) will be ignored. If variable names partly coincide with any of these names, or with count, res, geometry, it is necessary to specify vars.

The multi-resolution grids must be passed as named parameters if more than two are given.

Common variable names in different grids should be avoided.

The default of the function is to treat NA-values as zeroes when merging (through na.rm in sums). It will therefore not be possible to separate restricted grid cells from grid cells with zero observations after merging, except for the ones that have been left as they were. The alternative would be a much higher number of NA-values in the merged grids.

The resulting grid will most likely not have exactly the same values as a multi-resolution grid produced directly from the microdata. If the input-grids have been post-processed (the normal situation when not having access to the microdata), the grid cell values have usually been rounded, and some might have been suppressed. As these rounded and potentially suppressed values are summed, their values are likely to deviate from those that are computed directly from the microdata through a joint gridding process.

Examples

library(sf)

# These are SYNTHETIC agricultural FSS data 
data(ifs_dk) # Census data
ifs_weight = ifs_dk %>% dplyr::filter(Sample == 1) # Extract weighted subsample

# Create spatial data
ifg = fssgeo(ifs_dk, locAdj = "LL")
fsg = fssgeo(ifs_weight, locAdj = "LL")

# We use the numeric part of the farmtype to create a third variable. This 
# is done for the an example, the value does not have any meaning when treated 
# like this
ifg$ft = as.numeric(substr(ifg$FARMTYPE, 3, 4))^2

ress = c(1,5,10,20,40, 80, 160)*1000
# Create regular grid of the variables
ifl = gridData(ifg, vars = c("UAA", "UAAXK0000_ORG", "ft"), res = ress)

# Create the different multi-resolution grids
himg1 = multiResGrid(ifl, vars = "UAA", ifg = ifg, postProcess = FALSE)
himg2 = multiResGrid(ifl, vars = "UAAXK0000_ORG", ifg = ifg, postProcess = FALSE)
himg3 = multiResGrid(ifl, vars = "ft", ifg = ifg, postProcess = FALSE)

# The grids have different number of polygons
dim(himg1)
dim(himg2)
dim(himg3)

hh1 = MRGmerge(himg1, himg2, himg3 = himg3)
dim(hh1)
# Postprocessing can also be done on the merged object
hh11 = MRGmerge(himg1, himg2, himg3 = himg3, postProcess = TRUE, rounding = -1)
dim(hh11)
summary(hh1$UAA-hh11$UAA)

# Try to avoid having the same variable names in two different multi-resolution grids,
# although it works in this case

himg21 = multiResGrid(ifl, vars = c("UAA", "UAAXK0000_ORG"), ifg = ifg, postProcess = FALSE)
hh3 = MRGmerge(himg1, himg21, himg3 = himg3)
summary(hh3[, c("UAA", "UAA.1")])

himg4 = multiResGrid(ifl, vars = c("UAA", "ft", "UAAXK0000_ORG"), ifg = ifg, postProcess = FALSE)
summary(hh1[, c("UAA", "UAAXK0000_ORG", "ft")])
summary(himg4[, c("UAA", "UAAXK0000_ORG", "ft")])

           
           

MRG documentation built on Oct. 28, 2024, 5:07 p.m.