visual structure of a data.frame: locations of NAs and much more

Question

I want to represent the structure of a data frame (or matrix, or data.table whatever) on a single plot with color-coding. I guess that could be very useful for many people handling various types of data, to visualize it in a single glance.

Perhaps someone have already developed a package to do it, but I couldn't find one (just this). So here is a rough mockup of my "vision", kind of a heatmap, showing in color codes:

• the NA locations,
• the class of variables (factors (how many levels?), numeric (with color gradient, zeros, outliers...), strings)
• dimensions
• etc.....

So far I have just written a function to plot the NA locations it goes like this:

ggSTR = function(data, alpha=0.5){
  require(ggplot2)
  DF <- data
  if (!is.matrix(data)) DF <- as.matrix(DF)

  to.plot <- cbind.data.frame('y'=rep(1:nrow(DF), each=ncol(DF)), 
                              'x'=as.logical(t(is.na(DF)))*rep(1:ncol(DF), nrow(DF)))
  size <- 20 / log( prod(dim(DF)) )  # size of point depend on size of table
  g <- ggplot(data=to.plot) + aes(x,y) +
        geom_point(size=size, color="red", alpha=alpha) +
        scale_y_reverse() + xlim(1,ncol(DF)) +
        ggtitle("location of NAs in the data frame")

  pc <- round(sum(is.na(DF))/prod(dim(DF))*100, 2) # % NA
  print(paste("percentage of NA data: ", pc))

  return(g)
}

It takes any data.frame in input and returns this image:

It's too big a challenge for me to achieve the first image.

Answer 1

You can try out visdat package(https://github.com/ropensci/visdat), which shows the NA values and data types in the plot

install.packages("visdat")
library(visdat)
vis_dat(airquality)