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After the previous post on the packcircles package for R someone suggested it would be useful to be able to fix the position of selected circles. As a first attempt, I’ve added an optional `weights` argument to the `circleLayout` function. Weights can be in the range 0-1 inclusive, where a weight of 0 prevents a circle from moving, while a weight of 1 allows full movement. The updated code is at GitHub.

Here’s an example where the largest of a set of initially overlapping circles is fixed in place:

And here is the code for the example:

`<br />library(packcircles)<br />library(ggplot2)<br />library(gridExtra)<br /><br /># Generate some random overlapping circles<br />ncircles <- 200<br />limits <- c(-50, 50)<br />inset <- diff(limits) / 3<br />rmax <- 20<br /><br />xyr <- data.frame(<br />  x = runif(ncircles, min(limits) + inset, max(limits) - inset),<br />  y = runif(ncircles, min(limits) + inset, max(limits) - inset),<br />  r = rbeta(ncircles, 1, 10) * rmax)<br /><br /># Index of the largest circle<br />largest.id <- which(xyr\$r == max(xyr\$r))<br /><br />## Generate plot data for the `before` layout<br />dat.before <- circlePlotData(xyr)<br /><br /># Add a column to the plot data for the 'before' circles<br /># to indicate whether a circle is static of free to move<br />dat.before\$state <- ifelse(dat.before\$id == largest.id, "static", "free")<br /><br /># Run the layout algorithm with a weights vector to fix the position<br /># of the largest circle<br />wts <- rep(1.0, nrow(xyr))<br />wts[ largest.id ] <- 0.0<br /><br />res <- circleLayout(xyr, limits, limits, maxiter = 1000, weights=wts)<br /><br /># A plot function to colour circles based on the state column<br />doPlot <- function(dat, title)<br />  ggplot(dat) + <br />  geom_polygon(aes(x, y, group=id, fill=state), colour="brown1") +<br />  scale_fill_manual(values=c("NA", "brown4")) +<br />  coord_equal(xlim=limits, ylim=limits) +<br />  theme_bw() +<br />  theme(axis.text=element_blank(),<br />        axis.ticks=element_blank(),<br />        axis.title=element_blank(),<br />        legend.position="none") +<br />  labs(title=title)<br /><br />g.before <- doPlot(dat.before, "before")<br /><br /># Generate a plot for the 'after' circles<br />dat.after <- circlePlotData(res\$layout)<br />dat.after\$state <- ifelse(dat.after\$id == largest.id, "static", "free")<br /><br />g.after <- doPlot(dat.after, "after")<br /><br />grid.arrange(g.before, g.after, nrow=1)<br />`