Obtain a partition using a Greedy-type algorithm
Source:R/partition_tdv_grdtp.R
partition_tdv_grdtp.RdThis function obtains a partition of the columns of a given phytosociological matrix, aiming at high values of the Total Differential Value (TDV), implementing a Greedy-type algorithm.
Arguments
- m_bin
A matrix. A phytosociological table of 0s (absences) and 1s (presences), where rows correspond to taxa and columns correspond to relevés.
- k
A numeric giving the number of desired groups.
- verify
A logical. If
TRUE(the default) the function verifies if basic features ofm_bindata structure are met. Otherwise ifFALSE.
Value
A numeric vector, which length is the same as the number of columns
of m_bin, with numbers from 1 to k, representing the group to which the
respective column was ascribed.
Details
Given the phytosociological table m_bin (rows corresponding to
taxa and columns corresponding to relevés), this function uses a
Greedy-type algorithm (a simplified version of the Greedy algorithm) to
obtain a k-partition (k, defined by the user) of the columns of
m_bin, aiming at high values of TDV.
The algorithm operates in the following way: Firstly, k columns are
selected randomly to work as seeds for each one of the desired k groups.
Secondly, one of the remaining columns is selected randomly and added to
the partition group which maximizes the upcoming TDV. This second step is
repeated until all columns are placed in a group of the k-partition.
This function is expected to perform faster than partition_tdv_grasp(),
yet returning worse partitions in terms of TDV. For the (true) Greedy
algorithm see partition_tdv_grasp().
See tdv() for an explanation on the TDV of a phytosociological table.
Author
Jorge Orestes Cerdeira and Tiago Monteiro-Henriques. E-mail: tmh.dev@icloud.com.
Examples
# Getting the Taxus baccata forests data set
data(taxus_bin)
# Obtaining a partiton based on a Greedy-type algorithm
partition_tdv_grdtp(taxus_bin, 3)
#> [1] 1 1 1 1 1 1 1 1 2 1 1 1 1 1 2 3 3 3 3 3 2 3 2 3 3 3 3 3 3 3 3 3 3