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help for traces                                            Jean-Benoit Hardouin
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Graphical representations of the traces of dichotomous and polytomous items

        traces varlist [, score restscore ci test cumulative logistic
              repfile(directory) scorefiles(string) restscorefiles(string)
              logisticfile(string) nodraw nodrawcomb replace onlyone(varname)
              thresholds(string)]


Description

    traces builds graphical representations of various kinds of traces (non
        parametric Item Response Functions) for dichotomous or polytomous
        items.

Options

    score displays the graphical representations of the traces of the items
        as a function of the total score. This is the defaut option if none
        score, none restscore, none logistic are indicated.

    restscore displays the graphical representations of the traces of the
        items as a function of the rest-score (total score unless the item).

    ci displays the confidence interval at 95% of the traces.

    test tests the nullity of the slope of dichotomous items traces with a
        linear model.

    cumulative displays cumulative traces for polytomous items instead of
        classical traces.

    logistic displays the graphical representation of the logitic traces of
        the items as a function of the score: each trace is the result of a
        logistic model with the response to the item as variable to explicate
        and the score (and a constant) as explicative variable. This kind of
        trace is possible only for dichotomous items. All the logistic traces
        are represented in the same graph.

    repfile(directory) is the directory where the files are saved.

    scorefiles(string) defines the generic name of the files containing the
        graphical representations of the traces as a function of the score.
        The name will be followed by the name of each item and by the .gph
        extension. If this option is not indicated, the corresponding graphs
        will be not saved.

    restscorefiles(string) defines the generic name of the files containing
        the graphical representations of the traces as a function of the
        rest-scores.  The name will be followed by the name of each item and
        by the .gph extension. If this option is not indicated, the
        corresponding graphs will be not saved.

    logisticfile(string) defines the name of the file containing the
        graphical representations of the logistic traces. This name will be
        followed by the .gph extension.  If this option is not indicated, the
        corresponding graph will be not saved.

    nodraw does not display the graphs by items.

    nodrawcomb does not display the combined graphs by items.

    replace replaces graphical files when they already exist.

    onlyone displays only the trace of a given item.

    thresholds groups the individuals as a function of the (rest-)score. The
        string contains the maximal values of the (rest-)score in each group.



Example

        
    . traces item1 item2 item3 item4 , score repfile(c:\graphs)
        scorefiles(score) nodraw nodrawcomb replace /*creates the graphs
        files of the traces as a function of the score but do not display
        them.*/

        
    . traces item1 item2 item3 item4 , score restscore /*displays the
        graphical representations of the traces of the items as a function of
        the score and of the rest-scores, but does not save them*/

        
    . traces itemA* /*displays the graphical representations of the traces of
        the items as a function of the score, by default*/

        
    . traces itemA* ,only(itemA2) thresholds(2 3 5)/*displays the graphical
        representations of the traces of the item A2 as a function of the
        score. Individuals are grouped: a first group of individuals with
        scores from 0 to 2, a second group with a score of 3, a third group
        with a score between 4 and 5 and a last group with a score superior
        to 5*/

Author

    Jean-Benoit Hardouin, PhD, assistant professor
    Team of Biostatistics, Clinical Research and Subjective Measures in
        Health Sciences
    University of Nantes - Faculty of Pharmaceutical Sciences
    1, rue Gaston Veil - BP 53508
    44035 Nantes Cedex 1 - FRANCE
    Email:  jean-benoit.hardouin@univ-nantes.fr
    Websites AnaQol and FreeIRT

Also see

    Online: help for graph, loevH and gengroup if installed.