

   PPeeaarrssoonn''ss CChhii--ssqquuaarree TTeesstt ffoorr CCoouunntt DDaattaa

        chisq.test(x, y = NULL, correct = TRUE,
                   p = rep(1/length(x), length(x)))

   AArrgguummeennttss::

          x: a vector or matrix.

          y: a vector; ignored if `x' is a matrix.

    correct: a logical indicating whether to apply continuity
             correction when computing the test statistic.

   DDeessccrriippttiioonn::

        `chisq.test' performs chi-square tests on contingency
        tables.

   DDeettaaiillss::

        If `x' is a matrix with one row or column, or if `x' is
        a vector and `y' is not given, `x' is treated as a one-
        dimensional contingency table.  In this case, the
        hypothesis tested is whether the population probabili-
        ties equal those in `p', or are all equal if `p' is not
        given.

        If `x' is a matrix with at least two rows and columns,
        it is taken as a two-dimensional contingency table, and
        hence its entries should be nonnegative integers.  Oth-
        erwise, `x' and `y' must be vectors or factors of the
        same length; incomplete cases are removed, the objects
        are coerced into factor objects, and the contingency
        table is computed from these.  Then, Pearson's chi-
        square test of the null that the joint distribution of
        the cell counts in a 2-dimensional contingency table is
        the product of the row and column marginals is per-
        formed.  Continuity correction is only used in the
        2-by-2 case if `correct' is `TRUE'.

   VVaalluuee::

        A list with class `"htest"' containing the following
        components:

   statistic: the value the chi-square test statistic.

   parameter: the degrees of freedom of the approximate chi-
             square distribution of the test statistic.

    p.value: the p-value for the test.

     method: a character string indicating the type of test
             performed, and whether continuity correction was
             used.

   data.name: a character string giving the name(s) of the
             data.

   observed: the observed counts.

   expected: the expected counts under the null hypothesis.

   EExxaammpplleess::

        data(insects)                   # Not really a good example
        chisq.test(insects$count > 7, insects$spray)
                                        # Prints test summary
        chisq.test(insects$count > 7, insects$spray)$obs
                                        # Counts observed
        chisq.test(insects$count > 7, insects$spray)$obs
                                        # Counts expected under the null

