R/measureRule.R

In inTrees: Interpret Tree Ensembles

measureRule <-
function(ruleExec,X,target,pred=NULL,regMethod="mean"){
  len <- length(unlist(strsplit(ruleExec, split=" & ")))
  origRule <- ruleExec
  ruleExec <- paste("which(", ruleExec, ")")
  ixMatch <- eval(parse(text=ruleExec)) 
  if(length(ixMatch)==0){
    v <- c("-1","-1", "-1", "", "")
    names(v) <- c("len","freq","err","condition","pred")
    return(v)
  }
  ys <- target[ixMatch]
  freq <- round(length(ys)/nrow(X),digits=3)

  if(is.numeric(target))
  {
      if(regMethod == "median"){
        ysMost = median(ys)
      }else{
        ysMost <- mean(ys)
      }
      err <- sum((ysMost - ys)^2)/length(ys)   
  }else{ 
    if(length(pred)>0){ #if pred of the rule is provided
      ysMost = as.character(pred)
    }else{
      ysMost <- names(which.max(  table(ys))) # get back the first max
    }
    ly <- sum(as.character(ys)==ysMost)
    conf <- round(ly/length(ys),digits=3)    
    err <- 1 - conf
  }
  rule <- origRule

  v <- c(len, freq, err, rule, ysMost)
  names(v) <- c("len","freq","err","condition","pred")
  return(v)
}