R/denormalize.R
denormalize.RdCreate a (redundant) horizon-level attribute from a site-level attribute. Specify a SoilProfileCollection and a site-level attribute from that SPC (by name) to receive a vector of length equal to the number of horizons containing the site-level values. This vector is directly usable with the SoilProfileCollection horizon setter.
denormalize is the inverse operation for the formula interface that "normalizes" a horizon level variable to site level:
site(object) <- ~ horizonvar
denormalize(object, attr)A vector of values of equal length to the number of rows in the horizon table of the input SPC.
"Denormalization" is the process of trying to improve the read performance of a database, at the expense of losing some write performance, by adding redundant copies of data or by grouping data. Sometimes it is beneficial to have site-level attributes denormalized for grouping of horizon-level data in analyses. denormalize achieves this result for SoilProfileCollections.
data(sp1)
# create a SoilProfileCollection from horizon data
depths(sp1) <- id ~ top + bottom
# create random site-level attribute `sitevar` with a binary (0/1) outcome
sp1$sitevar <- round(runif(length(sp1)))
# use denormalize() to create a mirror of sitevar in the horizon table
# name the attribute something different (e.g. `hz.sitevar`) to
# prevent collision with the site attribute
# the attributes can have the same name but you will then need
# site() or horizons() to access explicitly
sp1$hz.sitevar <- denormalize(sp1, 'sitevar')
# compare number of profiles to number of sitevar assignments
length(sp1)
#> [1] 9
table(sp1$sitevar)
#>
#> 0 1
#> 3 6
# compare number of horizons to number of horizon-level copies of sitevar `hz.'sitevar`
nrow(sp1)
#> [1] 60
table(sp1$hz.sitevar)
#>
#> 0 1
#> 20 40