[R] help: how to plot a circle on the scatter plot

[Mulholland, Tom]

You will find previous discussion about pairs in this list. There are limits on what has been included within the functionality, but you can write your own panel functions. Here's a starting point.

x <- runif(100)
dim(x) <- c(20,5)

panel.cor1 <- function(x,y,...){
  mycor<- cor(x,y)
  if (mycor > 0){
  points(x,y, pch = 20, col = "red",cex = 0.5)
  } else {
  points(x,y, pch = 20, col = "grey",cex = 0.5)
  }
}

panel.cor2 <- function(x,y,...){
  mycor<- cor(x,y)
  if (mycor > 0){
  points(x,y, pch = 20, col = "blue",cex = 0.5)
  hpts <- chull(x,y)
  hpts <- c(hpts, hpts[1])
  lines(x[hpts],y[hpts],col = "red")
  } else {
  points(x,y, pch = 20, col = "grey",cex = 0.5)
  }
}


pairs(x,lower.panel = panel.cor1,upper.panel = panel.cor2)


Tom

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch
> [mailto:r-help-bounces at stat.math.ethz.ch]On Behalf Of wu sz
> Sent: Wednesday, 13 July 2005 9:48 AM
> To: questions about R
> Subject: [R] help: how to plot a circle on the scatter plot
> 
> 
> Hello,
> 
> I have a data set with 15 variables, and use "pairs" to plot the
> scatterplot of this data set. Then I want to plot some circles on the
> small pictures with high correlation(e.g. > 0.9).
> 
> First, I use "cor" to obtain the corresponding correlation matrix (x)
> for this scatterplot.
> 
> Second, use "seq(along = x)[x > 0.9]" to find the positions of the
> small pictures with 0.9 correlation, but "seq" can just find the
> sequence position row by row for the matrix, not a real position (like
> "rowNumber, colNumber"). Is any function for that?
> 
> Third, use "Symbols" to plot the circle on these small pictures, but
> seems it can't do that. Also, I don't know how to adjust the thickness
> and radius of the circle plotted by "Symbols".
> 
> Please give me some ideas!
> 
> Thank you,
> Shengzhe
> 
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