Plotting Andrews curves using dplyr and ggplot2

andrews.R

## https://en.wikipedia.org/wiki/Andrews_plot
library(dplyr)
library(ggplot2)

do.andrews <- function(x,breaks=30) {
  require(reshape2)
  
  t <- seq(-pi, pi, pi/breaks)
  m<-nrow(x)
  n<-ncol(x)
  
  f <- matrix(t,nrow=length(t),ncol=n)
  j <- seq(2,n)
  
  f[,j[j%%2==0]] <- sweep(f[,j[j%%2==0],drop=FALSE],
                          2,
                          j[j%%2==0]/2,
                          `*`)
  
  f[,j[j%%2!=0]] <- sweep(f[,j[j%%2!=0],drop=FALSE],
                          2,
                          j[j%%2!=0]%/%2,
                          `*`)
  f[,j[j%%2==0]] <- sin(f[,j[j%%2==0]])
  f[,j[j%%2!=0]] <- cos(f[,j[j%%2!=0]])
  
  f <- x[,j]%*%t(f[,j])
  f <- f+matrix(x[,1]/2^0.5,nrow=m,ncol=length(t),byrow=F)
  
  res <- melt(f,varnames=c('RowId','AndrewsId'),value.name = 'AndrewsValue')
  res[,'AndrewsId'] <- t[res[,'AndrewsId']]
  
  return(res)
}

iris %>%
  group_by(Species) %>%
  do({do.andrews(as.matrix(select(.,-Species)))}) %>%
  ggplot(aes(x=AndrewsId,y=AndrewsValue,color=Species,group=interaction(Species,RowId)))+
  geom_line(size=1.2)


iris %>%
  group_by(Species) %>%
  do({do.andrews(as.matrix(select(.,-Species)))}) %>%
  group_by(Species,AndrewsId) %>%
  summarize(AndrewsValue=mean(AndrewsValue)) %>%
  ggplot(aes(x=AndrewsId,y=AndrewsValue,color=Species))+
  geom_line(size=1.2)