How to group box-and-whisker in parallel for comparison in BoxWhiskerChart?

Question

I have two collections of data: xdata and ydata

xdata = { {"A", {1, 2, 5}}, {"B", {5, 7, 2, 2, 5}}, {"C", {3, 2, 5, 7}}};
ydata = { {"A", {7, 2}}, {"B", {7, 2, 5}}, {"C", {6, 7, 3}}};

Using BoxWhiskerChart, I can show xdata or ydata alone:

BoxWhiskerChart[xdata, 
 {{"Whiskers", Dashed}, {"Outliers", None}, {"MedianMarker", 1, Directive[Thick, White]}}, 
 PlotRange -> Automatic, ChartStyle -> 56, ImageSize -> Medium]

Now I want to group the data according to their labels (i.e., A, B, and C). The resulting figure (with the same faked data) is like this (in Python) @ stackoverflow:

Thus, my question is:

How to group box-and-whisker in parallel for comparison in BoxWhiskerChart?

In particular, how to show the labels (A, B, and C) in x-axis and how to draw the legends (xdata and ydata)?

Answer 1

There's an example exactly like this in the documentation for BoxWhiskerChart. All you need to do is reshape your data into a list of doubles:

xdata = {{"A", {1, 2, 5}}, {"B", {5, 7, 2, 2, 5}}, {"C", {3, 2, 5, 7}}};
ydata = {{"A", {7, 2}}, {"B", {7, 2, 5}}, {"C", {6, 7, 3}}};

labels = {xdata[[All, 1]], None}

xdata = xdata[[All, 2]];
ydata = ydata[[All, 2]];

data = Transpose@{xdata, ydata}

style = Sequence[{
  {"Whiskers", Dashed},
  {"Outliers", None},
  {"MedianMarker", 1, Directive[Thick, White]}},
  ChartStyle -> 56,
  ImageSize -> Medium,
  ChartLegends -> {"x", "y"},
  ChartLabels -> labels];

BoxWhiskerChart[data, style]