Module Hugin_kit.Stack

Stacks.

A stack lays lengths end to end. Each length belongs to a column, the x value of a bar or of the vertices of stacked areas, and to a series, the category or layer it is part of. Columns and series are numbered from 0: columns in the order of their x values, series in the order of their categories.

Within a column, the lengths that are not negative are laid upward from 0. and the negative ones downward from 0., in increasing series number, so positive and negative lengths never cancel. The extent of a column then runs from the end of its negative pile, lo, to the end of its positive pile, hi, with lo <= 0. <= hi. An offset then moves or scales each column.

intervals gives each length the interval it covers. A figure draws a stacked bar from the start of its interval to the end, and a stacked area between the starts and the ends of a series. A length that is nan or infinite is missing: it covers no interval, and its column is laid as if it were absent.

Stacks

#type offset = [

#| `Zero
(*
Each column's piles start at 0..
*)
#| `Expand
(*
Each column is scaled and moved so that its extent is [0;1]: lengths become fractions of their column's extent. A column whose extent is 0. to 0. is left as it is.
*)
#| `Center
(*
Each column is moved by -. (lo +. hi) /. 2., which centres its extent on 0..
*)

]

The type for stack offsets.

val intervals : 
  ?offset:offset ->
  columns:int array ->
  series:int array ->
  float array ->
  float array * float array

intervals ~offset ~columns ~series lengths is (starts, ends), where the length lengths.(r), in column columns.(r) and series series.(r), covers the interval from starts.(r) to ends.(r). In its pile, its start is the end of the length laid before it, or 0. for the first, and its end is its start plus itself, both then moved and scaled by offset. A pile lays its lengths by increasing series number, and the lengths of one series by increasing r. A missing length has nan as its start and end. Piles whose sums or extent exceed max_float give non-finite intervals. offset defaults to `Zero.

Raises Invalid_argument if columns, series and lengths differ in length or if a column or series number is negative.