plotSoilRelationGraph: Plot a component relation graph

In sharpshootR: A Soil Survey Toolkit

Description

Plot a component relation graph based on an adjacency or similarity matrix.

Usage

plotSoilRelationGraph(m, s='', plot.style='network', graph.mode='upper', 
spanning.tree=NULL, del.edges=NULL, vertex.scaling.factor=2, 
edge.scaling.factor=1, edge.transparency=1, edge.col=grey(0.5), 
edge.highlight.col='royalblue', 
g.layout=layout_with_fr,
...)

Arguments

m	adjacency matrix
s	central component; an empty character string is interpreted as no central component
plot.style	plot style ('network', or 'dendrogram'), or 'none' for no graphical output
graph.mode	interpretation of adjacency matrix: 'upper' or 'directed', see details
spanning.tree	plot the minimim or maximum spaning tree ('min', 'max'), or, max spanning tree plus edges with weight greater than the n-th quantile specified in 'spanning.tree'. See details and examples.
del.edges	optionally delete edges with weights less than the specified quantile (0-1)
vertex.scaling.factor	scaling factor applied to vertex size
edge.scaling.factor	optional scaling factor applied to edge width
edge.transparency	optional transparency setting for edges (0-1)
edge.col	edge color, applied to all edges
edge.highlight.col	edge color applied to all edges connecting to component named in s
g.layout	an igraph layout function, defaults to layout_with_fr
...	further arguments passed to plotting function

Details

Vertex size is based on a normalized index of connectivity: size = sqrt(degree(g)/max(degree(g))) * scaling.factor. Edge width can be optionally scaled by edge weight by specifying an edge.scaling.factor value. The maximum spanning tree represents a sub-graph where the sum of edge weights are maximized. The mimimum spanning tree represents a sub-graph where the sum of edge weights are minimized. The maximum spanning tree is likely a more useful simplification of the full graph, in which only the strongest relationships (e.g. most common co-occurrences) are preserved.

The maximum spanning tree + edges with weights > n-th quantile is an experimental hybrid. The 'backbone' of the graph is created by the maximum spanning tree, and augmented by 'strong' auxillary edges– defined by a value between 0 and 1.

The graph.mode argument is passed to igraph::graph_from_adjacency_matrix() and determines how vertex relationships are coded in the adjacency matrix m. Typically, the default value of 'upper' (the upper triangle of m contains adjacency information) is the desired mode. If m contains directional information, set graph.mode to 'directed'. This has the side-effect of altering the default community detection algorithm from igraph::cluster_fast_greedy to igraph::cluster_walktrap.

Value

an igraph 'graph' object is invisibly returned

Note

This function is a work in progress, ideas welcome.

Author(s)

D.E. Beaudette

Examples

# load sample data set
data(amador)

# create weighted adjacency matrix (see ?component.adj.matrix for details)
m <- component.adj.matrix(amador)

# plot network diagram, with Amador soil highlighted
plotSoilRelationGraph(m, s='amador')

# dendrogram representation
plotSoilRelationGraph(m, s='amador', plot.style='dendrogram')

# compare methods
m.o <- component.adj.matrix(amador, method='occurrence')

par(mfcol=c(1,2))
plotSoilRelationGraph(m, s='amador', plot.style='dendrogram')
title('community matrix')
plotSoilRelationGraph(m.o, s='amador', plot.style='dendrogram')
title('occurence')

# investigate max spanning tree
plotSoilRelationGraph(m, spanning.tree='max')

# investigate max spanning tree + edges with weights > 75-th pctile
plotSoilRelationGraph(m, spanning.tree=0.75)

## Not run: 
# get similar data from soilweb, for the Pardee series
s <- 'pardee'
u <- url(URLencode(paste(
'http://casoilresource.lawr.ucdavis.edu/soil_web/reflector_api/soils.php?',
'what=soil_series_component_query&q_string=', s, sep='')))

# fetch data
d <- read.table(u, sep='|', header=TRUE, stringsAsFactors=FALSE)

# normalize component names
d$compname <- tolower(d$compname)

# keep only major components
d <- subset(d, subset=compkind == 'Series')

# build adj. matrix and plot
m <- component.adj.matrix(d)
plotSoilRelationGraph(m, s=s, plot.style='dendrogram')

# alter plotting style, see ?plot.phylo
plotSoilRelationGraph(m, s=s, plot.style='dendrogram', type='fan')
plotSoilRelationGraph(m, s=s, plot.style='dendrogram', type='unrooted', use.edge.length=FALSE)

## End(Not run)

sharpshootR documentation built on May 2, 2019, 4:46 p.m.