README.md

In fbahoken/cartogRaflow: Filtering Matrix for Flow Mapping

Cartograflow

Filtering origin-destination Matrices for Thematic Flowmapping

This package is designed to filter origin-destination matrices for flow mapping purposes. It is based on different functions that are mainly used to prepare the flow dataset (pre-processing, filtering ...). It also allows to plot flows in the form of segments and arrows, to map and customize them (compatible sf & cartography).

Installation

Installing cartograflow CRAN version: install.packages("cartograflow")

To upgrade to the development version : See Follow up updates install.packages("devtools") library("devtools") remotes::install_github(url = "https://github.com/fbahoken/cartogRaflow")

Follow-up of updates

Work in progress : Coding of flowplaces() and flowlowup() for "M" format. Towards flow filtering for local point of view (major, dominant...).

[20/07/2020] cartograflow CRAN Update to 1.0.3 Updated functions : flowtype() New function : flowplace(), flowlowup()

[16/07/2020] flowlowup() flowlowup() (currently available for "L" format of matrix), is to extracts the upper or the lower triangular part of a matrix.

[05/06/2020] flowplaces() flowplace() (currently available for "L" format of matrix), is to compute flows margins indicators (on i,j) for places-based flow analysis.

[02/06/2020] cartograflow CRAN Update to 1.0.2 Suppression of the dependencies in the namespace files gdata and rgdal. Updated flowtype()

[1.0.0] cartograflow initial CRAN version

Available vignettes

\Vignette : rmd and html

Vignette cartograflow general presentation - CRAN version 1.0.3 subVignette : cartograflow concentration - v. 1.0.2 subVignette : cartograflow distance - v. 1.0.2 subVignette : cartograflow ordinal distance - v. 1.0.2

List of functions

1. Handling flow data

1.1. Pre-processing

-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.

1.2. Computing bilateral flows (on Fij)

Check if the matrix is close and square. See flowcarre() if not.

-flowtype() is to compute the main types of bilateral flows from an asymmetric flow dataset (matrice or long format). x = "flux" for remaining initial flow (Fij) or x = "transpose" for reverse flow value (Fji) or x = "bivolum" for bilateral volum as gross flow (FSij)=(Fij+Fji) or x = "bibal" for bilateral balance as net flow (FBij)=(Fij-Fji) or x = "biasym" for asymetry of bilateral flow (FSij)=(FBij/FSij) or x = "bimin" for (minFij)=(Fij, Fji) or x = "bimax" for (maxFij(Fij, Fji)) or x = "birange" for bilateral rangeFij=(maxFij - minFij) or x = "bidisym" for bilateral disymetry as (FDij)=(rangeFij/FSij).

For x = "bivolum": (or for symetric matrix) lowup = "up" for reducing the resulting matrix to the triangular sub-portion above the main diagonal lower = "low" for the sub-portion below the main diagonal

For x = "bibal": (or for antisymetric matrix) net = "positive" for extracting the positive flow values net = "negative" for extracting the negative flow values.

1.3. Computing flows places oriented indicators (on i or on j)

flowplaces()is to compute flow indicators from the margins of the matrix, e.g. on the flow's places of origin and/or destination.

x = "ini" for the number of incoming links (in-degree) or x = "outi" for the number of outcoming links (out-degree) or x = "degi" for the total number of links ini=(ini + outi) or x = "intra" for the total intra zonal interaction (if main diagonal is not empty) or x = "Oi" for the total flows emitted by (i) place or x = "Dj" for the total flows received by (j) place or x = "voli" for the total flow volume by place or x = "bali" for the net balance by place or x = "asyi" for the asymetry of flow by place or x = "allflowplaces" for computing all the above indicators.

2. Flow analysis

2.1. Concentration

flowgini() performs a concentration analysis of a flow dataset - To be use before flowanalysis() Computes Gini coefficient and plot Lorenz curve

flowanalysis() for computing a flow filter based on a double criterion for selecting flows before mapping.

See : subVignette : cartograflow concentration

2.2. Distance travelled

See : subVignette : cartograflow distance

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)

• if you choose the continous metric, you must first join your flows' dataset to a spatial shape, using flowjointure(), then use flowdist() as described below

2.2.1. 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 See : subVignette : cartograflow ordinal distance

flowcontig() is to compute an ordinal distance matrice based on a k-contiguity matrice.

3. Reducing an OD matrice

3.1. Reducing by extracting the lower / upper part of a matrix flowlowup() is to extracts the upper or the lower triangular part of a matrix - preferably for symmetrical matrixes.

x = "up" for the part above the main diagonal x = "low" for the part below the main diagonal.

3.2. Reducting a flow matrice by an external matrice flowreduct() is to reduce the flow dataset regarding another matrix, e.g. distances travelled.

metric is the metric of the distance matrix : - metric= continuous (e.g. for kilometers) - metric= ordinal (e.g. for k contiguity)

If metric = continuous (e.g for filtering flows by kilometric distances travelled), use: d.criteria is for selecting the minimum or the maximum distance criteria - d.criteria= dmin for keeping only flows up to a dmin criterion in km - d.criteria= dmax for selecting values less than a dmax criterion in km d is the value of the selected dmin or dmax criteria.

See : subVignette : cartograflow distance

4. Flow mapping

flowmap() is to plot flows as segments or arrows. Arguments are: filter is to filter or not flow's information or features threshold is used to set the filtering level of the flows when filter="True" taille is the value of the width of the flow feature a.head is the arrow head parameter 0: no arrow, 1:i->j, 2:i<-j, 3:i<->j. a.length is the length of the edges of the arrow head (in inches) a.angle is the angle from the shaft of the arrow to the edge of the arrow head a.col is the arrow's color plota is to add spatial features as map background to the flows's plot add is to allow to overlay flow features on external spatial features background

References : this comes after Bahoken, Françoise (2016), Contribution à la cartographie d'une matrice de flux, Thèse en Géographie - Siences des territoires, URL : https://halshs.archives-ouvertes.fr/tel-01273776.

See also: Tribute to Tobler(TTT)/Flowmapper - Work in progress

fbahoken/cartogRaflow documentation built on Oct. 15, 2021, 11:09 a.m.