grammar of graphics about trase HOT 4 CLOSED

I do like the idea of separating the data from the means of displaying it. At the moment we have the data copied into the plot1d class, you could imagine that you wanted two side by side plots of the same data set, so its a bit wasteful to have two copies of the data.

from trase.

The idea of the gog is that any plot is composed of these elementary parts:

• data and aesthetic mapping,
• a statistical transformation (stat),
• a geometric object (geom), and
• a position adjustment.

Translating the first three into classes:

class Data {
 // raw data set, can have any number of columns
 std::vector<std::vector<float>> data_matrix; 
};
class Aesthetic {
  int x; // column index for the x-axis
  int y;  // column index for the y-axis
  int colour; // column index to colour by
};
class Stat {
  std::shared_ptr<Data> original_data;
  Data transformed_data;
  Stat(Data *original_data) {
     // transform could be a histogram, for example
     transformed_data = transform(original_data); 
  }
};
enum Geom  = {Point, Line, Box, ...};
};

So each Plot1d could contain this set of elements

class Plot1d {
    // the Stat contains the original and transformed data
    // need a vector since we'll have one dataset for each frame
   std::vector<std::shared_ptr<Stat>> m_data;
   Aesthetic m_aes; // which columns to plot
   Geom m_geom; // how to plot them
   ...
};

@fcooper8472, what do you think about this layout?

from trase.

We've decided to implement this layout as is for the moment and see how it works.
Things to think about:

• user-facing API for sharing data/stats between plots
• 2d histograms: will it be slow drawing many squares for a 2d histogram versus drawing an image? Best to try it and find out
• Should Stat simply have an enum that swaps between transforms, or have derived classes implement each transform (going with an enum for now)
• Other aesthetics, e.g. opacity, size etc.

from trase.

many TODOs resulting from this, will create separate issues....

from trase.