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Filtering Matrices for Thematic Flowmapping - Dealing with “spaghetti-effect”
This package is designed to create the so-called
flowmaps, thematic origin-destination (OD) maps by
filtering matrices. It is based on different functions that are mainly
used to prepare the flow dataset. Complementary packages are for the
spatial objects processing sf package and for the mapping purposes
from{Cartography} except particular cases.
-flowcarre() is to transform an un-square to a square
matrice from a list of spatial objets ID (code).
-flowjointure() is to performs a spatial join between a
flow dataset and a map background.
-flowtabmat() is to transform a matrice format to a long
format and vice versa.
-flowstructmat() fixes an unpreviously ID shift in the
flow dataset “M” format. If necessary this function is to be used with
flowjointure() and flowtabmat.
It is to decide firstly to zero or not the diagonal, see
{base::diag}.
-flowtype() is to compute the main types of flows from
an asymmetric flow dataset (matrice or long format). The result is a
bilateral gross or bilateral net flows matrice. It is also possible to
compute the matrice’s margins in order to calculate probabilities of
sending and receiving flows or all kinds of indicators. Use for that the
R {base} or {dplyr}.
-flowgini() performs a concentration analysis of a flow
dataset - To be use before flowanalysis() Computes Gini
coefficient and plot Lorenz curve
-flowanalysis() is to be used after
flowgini() for computing a flow filter based on a
double criterion for selecting flows before mapping :
You have two ways to consider the distance travelled by flows : – if
you have a matrice distance, go directly to flowreduct() at
§2.2.3 ;
– if not, you can continue here, and have to choose the type of metric (continous or ordinal)
flowjointure(), then use
flowdist() as described below2.2.1. Compute continuous distances matrices
-flowjointure() performs an attribute spatial join - by
origin (i) and by destination (j) - between a flow dataset and a spatial
shape in order to transfert the origin-destination coordinates (Xi, Yi,
Xj, Yj) of the base map to the flow matrice.
-flowdist() Computes a continous distance
matrice choosing metric (rectilinear, euclidian, manhattan, …) before
using flowreduct() to filter the flow dataset.
2.2.2. Compute ordinal distances matrices
-flowcontig() compute an ordinal distance
distance matrice based on a k-contiguity matrice. (k) is the order
parameter, the number of borders to be crossed between origins and
destinations places. Use after flowreduct() and directly
flowmap()without applying the filter parameter. It is
possible to map firstly the k-order neighbourhood spatial graph
using flowmap() without applying the filter parameter.
2.2.3. Reducting a flow matrice by an external matrice
-flowreduct() is to perform the reduction of the flow
dataset according to another matrice (especially a matrice distance)
-flowmap() is to create a layer of lines and plot them,
using a flow dataset and a spatial shape.
References : this comes after Bahoken, Françoise (2016), Contribution à la cartographie d’une matrice de flux, Thèse en Géographie - Siences des territoires.
These binaries (installable software) and packages are in development.
They may not be fully stable and should be used with caution. We make no claims about them.
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