addGGArrows: Add Gradient Vector Arrows to Gradient Field Heatmap.

In kerschke/mogsa: A Multi-Objective Optimization Algorithm Based on Multi-Objective Gradients

Description

Add vectors indicating the gradient field to the heatmap of the cumulated path lengths.

Usage

addGGArrows(g, centers, gradients, fac = 0.025,
  arrow_len = unit(0.075/2, "inches"), nColumns = 10L, nRows = 10L,
  ...)

Arguments

g	[ggplot] ggplot-object as created by ggplotHeatmap.
centers	[matrix] Matrix containing the points of a grid of cells, for which the lengths of cumulated gradient paths should be computed. Each row corresponds to a single point.
gradients	[matrix] Matrix containing the multi-objective gradients for each point of centers.
fac	[numeric(1L)] Factor used for scaling the lengths of the gradient vectors. The default is 0.025.
arrow_len	[unit(1L)] Length of the arrow tips (default: unit(0.075 / 2, "inches")).
nColumns	[integer(1L)] How many columns of arrows should be drawn? The default is 10.
nRows	[integer(1L)] How many rows of arrows should be drawn? The default is 10.
...	[any] Further arguments to be passed to the geom_tile function of ggplot.

Value

[ggplot]
A ggplot object displaying the multi-objective gradient landscape.

Examples

# Define two single-objective test problems and a grid of points:
fn1 = function(x) sum((x - c(0.2, 1))^2)
fn2 = function(x) sum((x - c(0.5, 0.5))^2)
points = as.matrix(expand.grid(x1 = seq(0, 0.7, 0.005), x2 = seq(0, 1.25, 0.005)))

# Compute the corresponding gradients and the cumulated path lengths:
gradients = computeGradientField(points, fn1, fn2)
x = computeCumulatedPathLengths(points, gradients)

# Visualize the resulting multi-objective "landscape":
g = ggplotHeatmap(x)
g

# Add white arrows of the gradient field to the plot:
addGGArrows(g, points, gradients, color = "white")

kerschke/mogsa documentation built on July 11, 2019, 11:52 p.m.