## Archive for the ‘Stat. Graphics 101’ Category

### Understanding Area Based Plots: Trellis Displays

This is the third and last post on area based plots. Area based was certainly true for tree maps and mosaic plots, but falls a bit short for trellis displays, such that the term “grid based” would be more suitable. Nonetheless, all three plot types use conditioning within their core definition and the layout of […]

### Alpha Transparency explained

Once again the idea for this post was accelerated by a post on the JMP blog published some month ago. Alpha transparency was quite an eclectic feature in the mid 90s in statistics. I remember Ed Wegman visiting and presenting a video of what they accomplished with alpha transparency in parallel coordinates. The hardware they […]

### Understanding Area Based Plots: Mosaic Plots

Mosaic Plots are the swiss army knife of categorical data displays. Whereas bar charts are stuck in their univariate limits, mosaic plots and their variants open up the powerful visualization of multivariate categorical data. But let’s start with an introductory example. The Titanic data is still the most convincing application of mosaic plots, though many […]

### Understanding Area Based Plots: Tree Maps

Tree layouts are not too uncommon in statistics. CART is build upon tree hierarchies and random forrest uses these trees extensively. Area based plots like barcharts or histograms are also well understood by most statisticians. But when it comes to joining the two concepts – which will yield treemaps – many statisticians get somewhat lost. […]

### statistical graphics 101: Histograms

It’s been too long since the last posting (on barcharts) in the teaching corner. This one will be on histograms. Histograms are often mistaken with barcharts. The fundamental distinction between the two is Barcharts show counts (or weights) for the discrete axis of a categorical variable Histograms show an approximation of the density function (if […]

### statistical graphics 101: Barcharts

This month’s graphics is the Barchart. The barchart is used to visualize categorical data. It is often confused with the histogram, which can only be used if the data is continuous. The following barchart shows the distribution of all passengers of the Titanic according to their classes. All passengers who survived are highlighted in red. […]