Bubble Plots in R not displaying

Question

I was attempting to follow a tutorial to create a bubble plot of school district proficiency rates.

Data

shapefile of school districts (Census2010.shp)

District level data

Code

reading in data

dist <- read.csv('/Users/Path/to/District.csv', header = T)
state <- readShapePoly('/Users/Path/to/Census2010')

merge shapefile and district data

GA <- state
GA@data <-
    merge(GA@data, dist, by.x="NCESID", by.y="NCESID", all.x=T, sort=F )

creating bubble plot

plotvar <- GA@data$CCRPI
nclr <- 8
plotclr <- brewer.pal(nclr,"PuRd")
max.symbol.size=12
min.symbol.size=1
class <- classIntervals(plotvar, nclr, style="quantile") #Some school districts did not report data
colcode <- findColours(class, plotclr)
symbol.size <- ((plotvar-min(plotvar))/
    (max(plotvar)-min(plotvar))*(max.symbol.size - min.symbol.size) + min.symbol.size)
plot(GA)
GA.cntr <- coordinates(GA)
points(GA.cntr, pch=16, col = colcode, cex = symbol.size)
points(GA.cntr, cex = symbol.size)

Though the resulting map is just hollow school district outlines. What am I missing here?

Answer 1

This code seems to work. You cannot use merge on an sp dataframe object. Merge resorts the dataframes during its operation breaking the rownames and the internal relationship in the resulting sp object. I changed the code to use readOGR in rgdal to read the shapefile. You were also using some R internals as objects (i.e, dist, class). This confuses R and often causes errors.

I am using version(s) R 3.0.1, classInt 0.1-19, RColorBrewer 1.0-5, rgdal 0.8-9, and sp 1.0-9

Note: if you omit dividing by pi the bubbles are far too big to plot.

    require(sp)
    require(rgdal)
    require(RColorBrewer)
    require(classInt)

    setwd("D:/TEST/Bubble")
      sdist <- read.csv(paste(getwd(), "District.csv", sep="/"), header = T)
      state <- readOGR(getwd(), "Census2010")
        GA <- state

    # Merge sp dataframe
    merge.sp.df <- function(x, y, xcol, ycol) {
      x@data$sort <- 1:nrow(as(x@data, "data.frame"))  
        xdf <- as( x@data, "data.frame")
         xdf <- merge(xdf, y, by.x=xcol, by.y=ycol) 
           xdf <- xdf[order(xdf$sort), ]
             row.names(xdf) <- xdf$sort
          xdf <- xdf[,- which(names(xdf) == "sort")]     
        x@data <- xdf  
       return(x)
    }

    GA <- merge.sp.df(GA, sdist, "NCESID", "NCESID")   

    # create bubble plot
    plotvar <- GA@data$CCRPI
    nclr <- 8
    plotclr <- brewer.pal(nclr,"PuRd")
      max.symbol.size=12
      min.symbol.size=1

    qclass <- classIntervals(plotvar, nclr, style="quantile") 
      colcode <- findColours(qclass, plotclr)

GA@data$symbol.size <- ((GA@data$CCRPI-min(GA@data$CCRPI,na.rm=TRUE))/(max(GA@data$CCRPI,na.rm=TRUE)-
                         min(GA@data$CCRPI,na.rm=TRUE))*(max.symbol.size - min.symbol.size) + min.symbol.size)/pi
      pt.pch <- rep(16,dim(GA)[1])  
        pt.pch[which(is.na(GA@data$symbol.size))] <- NA

plot(GA)
  points(coordinates(GA), pch=pt.pch, col=colcode, cex=GA@data$symbol.size)
    legend("topright", legend=names(attr(colcode, "table")), pch=16, 
           col=unique(colcode)[2:nclr+1])