grid_jitter | R Documentation |
Data jittering reduces overplotting by adding small variances to values. grid_jitter removes it entirely by fitting points to a custom grid. This function applies Hungarian algorithm to match entire points set to the whole grid. (By contrast grid_jitter2 applies Hungarian with small area constraints.) This function works well for smaller grids and point sets, but will slow considerably with larger sets.
grid_jitter(x, y = NULL, nx = 50, ny = NULL, tol = 5, plotresults = TRUE, file = NULL, w = 20, h = 20)
x |
Numeric vector or 2 column matrix or data.frame of data points to plot |
y |
Numeric vector, y coordinates matching x (if a vector) |
nx |
Numeric, grid x/y dimensions |
ny |
Numeric |
tol |
Numeric, the maximum distance overplotted points are allowed to move to the nearest vacant grid cell |
plotresults |
Logical, output plots to illustrate point displacements and cell-reallocations |
file |
String, if not NULL the result of plotresults will save to filename instead of rendering in R |
w |
Numeric, width/height (inches) of plotresults if output to file (PDF) |
h |
Numeric |
A 2 column matrix of grid-jittered point coordinates
# 1. normal distribution d1 = data.frame(x = rnorm(300), y = rnorm(300)) d1g = grid_jitter(d1, nx=50, ny=50, tol=5) # 2. faithful dataset d2 = faithful d2g = grid_jitter(d2, nx=50, ny=50, tol=3) # 3. mpg example d3 = ggplot2::mpg[,c(3,8)] d3g = grid_jitter(d3, nx=100, ny=100, tol=3) # 4. US States d4 = data.frame(x=state.center$x, y=state.center$y, id=state.abb) d4j = grid_jitter(d4[,1:2], nx=10, ny=8, tol=3, plotresults=TRUE) cols = sample(colorRampPalette(c('darkblue','blue','lightblue'))(50)) par(mai=rep(.6,4), mfrow=c(1,2)) plot(d4[,1:2], pch=15, cex=2.5, col=cols, asp=2.5, xlab=NA, ylab=NA) text(d4[,1:2], labels=state.abb, col='white', cex=.7) plot(d4j, pch=15, cex=2.5, col=cols, asp=2.5, xlab=NA, ylab=NA) text(d4j, labels=d4$id, col='white', cex=.7) # 5. to illuste cell reallocation d5 = data.frame(x = c(1,rep(50, 398), 100), y = c(1,rep(50, 398), 100)) d5g = grid_jitter(d5, nx=30, ny=30, tol=15)
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