biogram (version 1.0)

fast_crosstable: Very fast 2d cross-tabulation

Description

Quickly cross-tabulates two binary vectors.

Usage

fast_crosstable(target_b, len_target, pos_target, feature)

Arguments

target_b

target in bits (as per as.bit).

len_target

length of target vector.

pos_target

number of positive cases in target vector.

feature

feature vector.

Value

• a vector of length four:
  1. target +, feature+
  2. target +, feature-
  3. target -, feature+
  4. target -, feature-

Details

Input looks odd, but the function was build to be as fast as possible subroutine of calc_ig, which works on many features but only one target.

Examples

tar <- sample(0L:1, 100, replace = TRUE)
feat <- sample(0L:1, 100, replace = TRUE)
library(bit) #used to code vector as bit
fast_crosstable(as.bit(tar), length(tar), sum(tar),  feat)