# The Collocation Tab

On this tab you can run statistical calculations against the current set of concordance lines you have on the Concordance Tab.

## The Display

The tab is divided into two areas. On the right the table of collocational data is displayed, and on the left are all the configuration options you can set to influence your calculation.

## The Actions

### Calculation Options

Evaluation Function
  There is a selection of different evaluation functions availble that you can choose from to analyse the data.
  - mutual information, the classical formula as initially described by Church & Hanks.
  - mi (double), mutual information with a weighting factor to boost the scores of more frequent words. This is to counterbalance the fact the mutual information often comes up with freak words as collocates due to their rareness.
  - mi (triple), mutual information with an even higher weight for frequent words.
  - t-score, the statistical t-test, as adapted by Church & Hanks. Scores better on high frequency words than the mutual information metric.
  - z-score, a rather old but tested metric.
  - observed/expected, the ratio of observed frequency over expected frequency.
  - log-likelihood and
  - modified log-likelihood, a measurement proposed by Adam Kilgarriff and Ted Dunning.
Enhancer
  You have two options to enhance your calculation.
  Direction
    for each word a distinction is made between its occurrences on the left or on the right of the node. This can often unveil asymmetrical distribution, when one side-occurrence gets a higher score than the combined (both sides).
  Case Fold
    When this option is selected, all words are collated to upper case. This is useful for combining accidentally capitalised words (eg at the beginning of a sentence), but can blur the distinction between proper nouns and common nouns.
Environment
  Two parameters to set here:
  Span
    The span defines how many words are taken into account for collecting the collocates on either side. The extent of the span can be chosen seperately for the left and the right.
  Cut-Off
    The cut-off allows you to exclude rare and freak words from the calculation. Words that occur rarely are often typographical errors or weird names, which usually get high scores due to their rareness. All words that do not occur more often than the specified value are ignored for the purpose of the calculation.
Calculate
  When you have set all the options you want, click calculate to produce a table of collocations.

### The Collocation Table

The table of collocations has five columns of information.

#
  The numeric rank of that collocate according to the score allocated by the evaluation function.
Collocate
  The word occuring as a collocate.
Joint Frequency
  The number of times that the collocate and the node word occur together within the span.
Total Frequency
  The total number of times that the collocate appears within the corpora selected.
Score
  The score allocated by the evaluation frequency.

## Sorting

When the table of collocations is created it is sorted according to the scoring method of the evaluation function. However, once the table has been created, you can sort it according to any column by clicking on the respective column header bar. If you press shift and click on the column header bar, the table will be sorted in reverse order.

You can therefore sort the collocational data as follows:

- according to joint or total frequency, in normal or reverse order.
- in alphabetical or reverse alphabetical order ( with the collocate column header bar)
- in numerical or reverse numerical order (with the # column header bar).

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