partition_tdv_grdtp {diffval} | R Documentation |
Obtain a partition using a Greedy-type algorithm
Description
This 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.
Usage
partition_tdv_grdtp(m_bin, k, verify = TRUE)
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 |
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.
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.
Author(s)
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)