Used to assess multi-calibration based on a list of
binary subgroup_masks passed during initialization.
list with items
corr: pseudo-correlation between residuals and learner prediction.
l: the trained learner.
Other AuditorFitter: 
CVLearnerAuditorFitter,
LearnerAuditorFitter,
SubpopAuditorFitter
mcboost::AuditorFitter -> SubgroupAuditorFitter
subgroup_maskslist 
List of subgroup masks.
Initialize a SubgroupAuditorFitter
Inherited methods
new()Initializes a SubgroupAuditorFitter that
assesses multi-calibration within each group defined
by the `subpops'.
SubgroupAuditorFitter$new(subgroup_masks)subgroup_maskslist 
List of subgroup masks. Subgroup masks are list(s) of integer masks,
each with the same length as data to be fitted on.
They allow defining subgroups of the data.
fit()Fit the learner and compute correlation
datadata.table
Features.
residnumeric
Residuals (of same length as data).
maskinteger
Mask applied to the data. Only used for SubgroupAuditorFitter.
 library("data.table")
 data = data.table(
   "AGE_0_10" =  c(1, 1, 0, 0, 0),
   "AGE_11_20" = c(0, 0, 1, 0, 0),
   "AGE_21_31" = c(0, 0, 0, 1, 1),
   "X1" = runif(5),
   "X2" = runif(5)
 )
 label = c(1,0,0,1,1)
 masks = list(
   "M1" = c(1L, 0L, 1L, 1L, 0L),
   "M2" = c(1L, 0L, 0L, 0L, 1L)
 )
 sg = SubgroupAuditorFitter$new(masks)