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orange-textable / docs / rst / counting_segment_types.rst

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File docs/rst/counting_segment_types.rst

 Counting segment types
 ======================
 
-In preparation.
+Widget :ref:`Count` takes in input one or more segmentations and
+produces frequency tables such as tables 1 and 2
+:doc:`here <segmentations_tables>`. To try it out, create a scheme such as
+illustrated on :ref:`figure 1 <counting_segment_types_fig1>` below. As usual,
+we will suppose that the :ref:`Text Field` instance contains
+*a simple example*. The :ref:`Segment` instance is configured for
+letter segmentation (**Regex:** *\\w* and **Output segmentation label:**
+*letters*). The default configuration of the instances of
+:ref:`Convert` and *Data Table* (from the **Data** tab of Orange
+Canvas) needs not be modified for this example.
+
+.. _counting_segment_types_fig1:
+
+.. figure:: figures/count_example_scheme.png
+    :align: center
+    :alt: Scheme for testing the Count widget
+    :figclass: align-center
+
+    Figure 1: Scheme for testing the :ref:`Count` widget.
+
+Basically, the purpose of widget :ref:`Count` is to determine the frequency
+of segment types in an input segmentation. The label of that segmentation must
+be indicated in the **Segmentation** menu of section **Units** in the widget's
+interface, while other controls may be left in their default state for now
+(see :ref:`figure 2 <counting_segment_types_fig2>` below). Clicking
+**Compute** then double-clicking the *Data Table* instance should display
+essentially the same data as table 1
+:ref:`here <segmentations_tables_table1>` (with possible variations in
+the order of columns).
+
+.. _counting_segment_types_fig2:
+
+.. figure:: figures/count_example.png
+    :align: center
+    :alt: Counting the frequency of letter types with widget :ref:`Count`
+    :figclass: align-center
+
+    Figure 2: Counting the frequency of letter types with widget :ref:`Count`.
+
+Note that checkbox *Compute automatically* is unchecked by default so that
+the user must click on **Compute** to trigger computations. The motivation for
+this default setting is that
+:doc:`table construction widgets <table_construction_widgets>` can be quite
+slow when operating on large segmentations, and it can be annoying to see
+computations starting again whenever an interface element is modified.
+
+To obtain the frequency of letter *bigrams* (i.e. pairs of successive
+letters), simply set parameter **Sequence length** to 2 (see
+:ref:`table 1 <counting_segment_types_table1>` below). If the value of this
+parameter is greated than 1, the string specified in field **Intra-sequence
+delimiter** is inserted between successive segments for the sake of
+readability--which is more useful when segments are longer than individual
+letters. Note that in this example, word boundaries are not taken into
+account--nor even known, in fact--which is why bigrams *as* and *ee* have a
+nonzero frequency.
+
+.. _counting_segment_types_table1:
+
+.. csv-table:: Table 1: Letter bigram frequency.
+    :header: *as*, *si*, *im*, *mp*, *pl*, *le*, *ex*, *xa*, *am*
+    :stub-columns: 0
+    :widths: 3 3 3 3 3 3 3 3 3
+
+    1,   1,   1,   2,   2,   2,   1,   1,   1
+
+
+