Investigate variable relations of a specific variable with mutual forest impact (corrected mean adjusted agreement).

This function corrects the mean adjusted agreement by a permutation approach and generates the relation parameter mutual forest impact. Subsequently p-values are determined and related variables are selected.

Usage

var.relations.mfi(
  x = NULL,
  y = NULL,
  num.trees = 500,
  type = "regression",
  s = NULL,
  mtry = NULL,
  min.node.size = 1,
  num.threads = NULL,
  status = NULL,
  save.ranger = FALSE,
  create.forest = is.null(forest),
  forest = NULL,
  save.memory = FALSE,
  case.weights = NULL,
  variables,
  candidates,
  p.t = 0.01,
  select.rel = TRUE,
  method = "janitza"
)

Arguments

x: data.frame of predictor variables with variables in columns and samples in rows (Note: missing values are not allowed)
y: vector with values of phenotype variable (Note: will be converted to factor if classification mode is used). For survival forests this is the time variable.
num.trees: number of trees. Default is 500.
type: mode of prediction ("regression", "classification" or "survival"). Default is regression.
s: predefined number of surrogate splits (it may happen that the actual number of surrogate splits differs in individual nodes). Default is 1 percent of no. of variables.
mtry: number of variables to possibly split at in each node. Default is no. of variables^(3/4) ("^3/4") as recommended by (Ishwaran 2011). Also possible is "sqrt" and "0.5" to use the square root or half of the no. of variables.
min.node.size: minimal node size. Default is 1.
num.threads: number of threads used for determination of relations. Default is number of CPUs available.
status: status variable, only applicable to survival data. Use 1 for event and 0 for censoring.
save.ranger: set TRUE if ranger object should be saved. Default is that ranger object is not saved (FALSE).
create.forest: Default: TRUE if forest is NULL, FALSE otherwise. Whether to create or use an existing forest.
forest: the random forest that should be analyzed
save.memory: Use memory saving (but slower) splitting mode. No effect for survival and GWAS data. Warning: This option slows down the tree growing, use only if you encounter memory problems. (This parameter is transfered to ranger)
case.weights: Weights for sampling of training observations. Observations with larger weights will be selected with higher probability in the bootstrap (or subsampled) samples for the trees.
variables: variable names (string) for which related variables should be searched for (has to be contained in allvariables)
candidates: vector of variable names (strings) that are candidates to be related to the variables (has to be contained in allvariables)
p.t: p.value threshold for selection of related variables. Default is 0.01.
select.rel: set False if only relations should be calculated and no related variables should be selected.
method: Method to compute p-values. Use "janitza" for the method by Janitza et al. (2016) or "permutation" to utilize permuted relations.

Value

A list containing:

variables: the variables to which relations are investigated.
surr.res: a matrix with the mutual forest impact values with variables in rows and candidates in columns.
surr.perm: a matrix with the mutual forest impact values of the permuted variables with variables in rows and candidates in columns.
p.rel: a list with the obtained p-values for the relation analysis of each variable.
var.rel: a list with vectors of related variables for each variable.
ranger: ranger objects.
method: Method to compute p-values: "janitza" or "permutation".
p.t: p.value threshold for selection of related variables

Examples

# \donttest{
data("SMD_example_data")
x <- SMD_example_data[, 2:ncol(SMD_example_data)]
y <- SMD_example_data[, 1]
# calculate variable relations
set.seed(42)
res <- var.relations.mfi(
  x = x,
  y = y,
  s = 10,
  num.trees = 10,
  variables = c("X1", "X7"),
  candidates = colnames(x)[1:100],
  num.threads = 1
)
#> Warning: Relations for 10 original variables were not calculated because they were never used as a primary split.
#>             Affected relations are set to 0. 
#> Warning: Relations for 12 permuted variables were not calculated because they were not used as a primary split.
#>             Affected relations are set to 0. 
res$var.rel[[1]]
#>  [1] "cp1_1"  "cp1_2"  "cp1_3"  "cp1_4"  "cp1_5"  "cp1_6"  "cp1_7"  "cp1_8" 
#>  [9] "cp1_9"  "cp1_10"
# }