Added documentation for the FACTOR command

diff --git a/doc/statistics.texi b/doc/statistics.texi
index 63e8f35aef9ba37f540661aee7018c3b6a9fadb4..cdc5fdf6706dee358a119e252273d0ce22caf4f3 100644 (file)
--- a/doc/statistics.texi
+++ b/doc/statistics.texi
@@ -10,6 +10,7 @@ far.
 * EXAMINE::                     Testing data for normality.
 * CORRELATIONS::                Correlation tables.
 * CROSSTABS::                   Crosstabulation tables.
 * EXAMINE::                     Testing data for normality.
 * CORRELATIONS::                Correlation tables.
 * CROSSTABS::                   Crosstabulation tables.

+* FACTOR::                      Factor analysis and Principal Components analysis

 * NPAR TESTS::                  Nonparametric tests.
 * T-TEST::                      Test hypotheses about means.
 * ONEWAY::                      One way analysis of variance.
 * NPAR TESTS::                  Nonparametric tests.
 * T-TEST::                      Test hypotheses about means.
 * ONEWAY::                      One way analysis of variance.


@@ -341,7 +342,7 @@ values are excluded as well as system-missing values.
 This is the default.
 
 If LISTWISE is set, then the entire case is excluded from analysis
 This is the default.
 
 If LISTWISE is set, then the entire case is excluded from analysis

-whenever any variable  specified in the any @cmd{/VARIABLES} subcommand
+whenever any variable  specified in any @cmd{/VARIABLES} subcommand

 contains a missing value.   
 If PAIRWISE is set, then a case is considered missing only if either of the
 values  for the particular coefficient are missing.
 contains a missing value.   
 If PAIRWISE is set, then a case is considered missing only if either of the
 values  for the particular coefficient are missing.


@@ -553,6 +554,99 @@ Approximate T of uncertainty coefficient is wrong.
 
 Fixes for any of these deficiencies would be welcomed.
 
 
 Fixes for any of these deficiencies would be welcomed.
 

+@node FACTOR
+@section FACTOR
+
+@vindex FACTOR
+@cindex factor analysis
+@cindex principal components analysis
+@cindex principal axis factoring
+@cindex data reduction
+
+@display
+FACTOR  VARIABLES=var_list
+
+        [ /METHOD = @{CORRELATION, COVARIANCE@} ]
+
+        [ /EXTRACTION=@{PC, PAF@}] 
+
+        [ /PRINT=[INITIAL] [EXTRACTION] [UNIVARIATE] [CORRELATION] [COVARIANCE] [DET] [SIG] [ALL] [DEFAULT] ]
+
+        [ /PLOT=[EIGEN] ]
+
+        [ /FORMAT=[SORT] [BLANK(@var{n})] [DEFAULT] ]
+
+        [ /CRITERIA=[FACTORS(@var{n})] [MINEIGEN(@var{l})] [ITERATE(@var{m})] [ECONVERGE (@var{delta})] [DEFAULT] ]
+
+        [ /MISSING=[@{LISTWISE, PAIRWISE@}] [@{INCLUDE, EXCLUDE@}] ]
+@end display
+
+The FACTOR command performs Factor Analysis or Principal Axis Factoring on a dataset.  It may be used to find
+common factors in the data or for data reduction purposes.
+
+The VARIABLES subcommand is required.  It lists the variables which are to partake in the analysis.
+
+The /EXTRACTION subcommand is used to specify the way in which factors (components) are extracted from the data.
+If PC is specified, then Principal Components Analysis is used.  If PAF is specified, then Principal Axis Factoring is
+used. By default Principal Components Analysis will be used.
+
+The /METHOD subcommand should be used to determine whether the covariance matrix or the correlation matrix of the data is
+to be analysed.  By default, the correlation matrix is analysed.
+
+The /PRINT subcommand may be used to select which features of the analysis are reported:
+
+@itemize
+@item UNIVARIATE
+      A table of mean values, standard deviations and total weights are printed.
+@item INITIAL
+      Initial communalities and eigenvalues are printed.
+@item EXTRACTION
+      Extracted communalities and eigenvalues are printed.
+@item CORRELATION
+      The correlation matrix is printed.
+@item COVARIANCE
+      The covariance matrix is printed.
+@item DET
+      The determinant of the correlation or covariance matrix is printed.
+@item SIG
+      The significance of the elements of correlation matrix is printed.
+@item ALL
+      All of the above are printed.
+@item DEFAULT
+      Identical to INITIAL and EXTRACTION.
+@end itemize
+
+If /PLOT=EIGEN is given, then a ``Scree'' plot of the eigenvalues will be printed.  This can be useful for visualising
+which factors (components) should be retained.
+
+The /FORMAT subcommand determined how data are to be displayed in loading matrices.  If SORT is specified, then the variables
+are sorted in descending order of significance.  If BLANK(@var{n}) is specified, then coefficients whose absolute value is less
+than @var{n} will not be printed.  If the keyword DEFAULT is given, or if no /FORMAT subcommand is given, then no sorting is 
+performed, and all coefficients will be printed.
+
+The /CRITERIA subcommand is used to specify how the number of extracted factors (components) are chosen.  If FACTORS(@var{n}) is
+specified, where @var{n} is an integer, then @var{n} factors will be extracted.  Otherwise, the MINEIGEN setting will
+be used.  MINEIGEN(@var{l}) requests that all factors whose eigenvalues are greater than or equal to @var{l} are extracted.
+The default value of @var{l} is 1.    The ECONVERGE and ITERATE settings have effect only when iterative algorithms for factor
+extraction (such as Principal Axis Factoring) are used.   ECONVERGE(@var{delta}) specifies that iteration should cease when
+the maximum absolute value of the communality estimate between one iteration and the previous is less than @var{delta}. The
+default value of @var{delta} is 0.001.
+The ITERATE(@var{m}) setting sets the maximum number of iterations to @var{m}.  The default value of @var{m} is 25.
+
+The @cmd{MISSING} subcommand determines the handling of missing variables.  
+If INCLUDE is set, then user-missing values are included in the
+calculations, but system-missing values are not.
+If EXCLUDE is set, which is the default, user-missing
+values are excluded as well as system-missing values. 
+This is the default.
+If LISTWISE is set, then the entire case is excluded from analysis
+whenever any variable  specified in the @cmd{VARIABLES} subcommand
+contains a missing value.   
+If PAIRWISE is set, then a case is considered missing only if either of the
+values  for the particular coefficient are missing.
+The default is LISTWISE.
+ 
+

 @node NPAR TESTS
 @section NPAR TESTS
 
 @node NPAR TESTS
 @section NPAR TESTS