gplot {GSD}

Plot of a Graph Signal

Description

This function displays a signal on a graph using a color palette.

Usage

gplot(graph, signal = NULL, size = 1, limits = range(V(graph)$z), 
    gpalette = NULL, legend = TRUE)

Arguments

graph

an igraph graph object with vertex attributes of coordinates x, y, a signal z, and edge attribute of weight.

signal

specifies a signal to be displayed over object graph using a color palette. When signal=NULL, a signal z of object graph is used.

size

specifies point size of vertex.

limits

specifies color palette limits.

gpalette

specifies a character vector of color palette. When gpalette=NULL, c('#00008D', '#002AFF', '#00D4FF', '#2AFFD4', '#FFFF00', '#FF8D00', '#FF0000') is used as default palette.

legend

if legend=FALSE, the legend is not included.

Details

This function displays a signal on a graph using a color palette.

Value

plot of a signal over a graph using package ggplot2.

See Also

gsignal, adjmatrix.

Examples

#### example : composite of two components having different frequencies

## define vertex coordinate
x <- y <- seq(0, 1, length=30)
xy <- expand.grid(x=x, y=y)

## weighted adjacency matrix by Gaussian kernel 
## for connecting vertices within distance 0.04
A <- adjmatrix(xy, method = "dist", 0.04) 

## signal
# high-frequency component
signal1 <- rep(sin(12.5*pi*x - 1.25*pi), 30)

# low-frequency component
signal2 <- rep(sin(5*pi*x - 0.5*pi), 30)

# composite signal
signal0 <- signal1 + signal2

# noisy signal with SNR(signal-to-noise ratio)=5
signal <- signal0 + rnorm(900, 0, sqrt(var(signal0) / 5)) 

# graph with signal
gsig <- gsignal(vertex = cbind(xy, signal), edge = A, edgetype = "matrix")

# display a signal over graph with legend
gplot(gsig, size=3, legend=TRUE) 

# display a signal over graph without legend
gplotout <- gplot(gsig, size=3, legend=FALSE) 
gplotout

# adding labels using ggplot2 package
gplotout + 
  theme(axis.title=element_text(), 
    plot.title=element_text(hjust = 0.5, vjust = 0)) + 
    labs(x="x", y="y", title="visualization of a composite signal")

# deleting axis title, text and ticks using ggplot2 package
gplotout + 
  theme(axis.title=element_blank(),
        axis.text=element_blank(),
        axis.ticks=element_blank())

# display high-frequency component
gplot(gsig, signal1, size=3, legend=FALSE) 

# display low-frequency component
gplot(gsig, signal2, size=3, legend=FALSE)