X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=doc%2Fstatistics.texi;h=3877a8d43d93db8ddd35a49aa287121ac907bd86;hb=6e80abcaeb7c361477eff4b8a578e54f1def81c4;hp=ac3f0b5c06f64e97df1f27417a0ccb67c4ff6881;hpb=56d6f17c81105cffb326be040430fefe53f95eea;p=pspp diff --git a/doc/statistics.texi b/doc/statistics.texi index ac3f0b5c06..3877a8d43d 100644 --- a/doc/statistics.texi +++ b/doc/statistics.texi @@ -411,8 +411,9 @@ large quantity of output. @display GRAPH - /HISTOGRAM = @var{var} - /SCATTERPLOT [(BIVARIATE)] = @var{var1} WITH @var{var2} [BY @var{var3}] + /HISTOGRAM [(NORMAL)]= @var{var} + /SCATTERPLOT [(BIVARIATE)] = @var{var1} WITH @var{var2} [BY @var{var3}] + /BAR = @{@var{summary-function}(@var{var1}) | @var{count-function}@} BY @var{var2} [BY @var{var3}] [ /MISSING=@{LISTWISE, VARIABLE@} [@{EXCLUDE, INCLUDE@}] ] [@{NOREPORT,REPORT@}] @@ -422,11 +423,20 @@ The @cmd{GRAPH} produces graphical plots of data. Only one of the subcommands @subcmd{HISTOGRAM} or @subcmd{SCATTERPLOT} can be specified, i.e. only one plot can be produced per call of @cmd{GRAPH}. The @subcmd{MISSING} is optional. +@menu +* SCATTERPLOT:: Cartesian Plots +* HISTOGRAM:: Histograms +* BAR CHART:: Bar Charts +@end menu + +@node SCATTERPLOT +@subsection Scatterplot @cindex scatterplot -The subcommand @subcmd{SCATTERPLOT} produces an xy plot of the data. The different -values of the optional third variable @var{var3} will result in different colours and/or -markers for the plot. The following is an example for producing a scatterplot. +The subcommand @subcmd{SCATTERPLOT} produces an xy plot of the +data. The different values of the optional third variable @var{var3} +will result in different colours and/or markers for the plot. The +following is an example for producing a scatterplot. @example GRAPH @@ -437,10 +447,14 @@ This example will produce a scatterplot where @var{height} is plotted versus @va on the value of the @var{gender} variable, the colour of the datapoint is different. With this plot it is possible to analyze gender differences for @var{height} vs.@: @var{weight} relation. +@node HISTOGRAM +@subsection Histogram @cindex histogram The subcommand @subcmd{HISTOGRAM} produces a histogram. Only one variable is allowed for the histogram plot. +The keyword @subcmd{NORMAL} may be specified in parentheses, to indicate that the ideal normal curve +should be superimposed over the histogram. For an alternative method to produce histograms @pxref{EXAMINE}. The following example produces a histogram plot for the variable @var{weight}. @@ -449,6 +463,60 @@ GRAPH /HISTOGRAM = @var{weight}. @end example +@node BAR CHART +@subsection Bar Chart +@cindex bar chart + +The subcommand @subcmd{BAR} produces a bar chart. +This subcommand requires that a @var{count-function} be specified (with no arguments) or a @var{summary-function} with a variable @var{var1} in parentheses. +Following the summary or count function, the keyword @subcmd{BY} should be specified and then a catagorical variable, @var{var2}. +The values of the variable @var{var2} determine the labels of the bars to be plotted. +Optionally a second categorical variable @var{var3} may be specified in which case a clustered (grouped) bar chart is produced. + +Valid count functions are +@table @subcmd +@item COUNT +The weighted counts of the cases in each category. +@item PCT +The weighted counts of the cases in each category expressed as a percentage of the total weights of the cases. +@item CUFREQ +The cumulative weighted counts of the cases in each category. +@item CUPCT +The cumulative weighted counts of the cases in each category expressed as a percentage of the total weights of the cases. +@end table + +The summary function is applied to @var{var1} across all cases in each category. +The recognised summary functions are: +@table @subcmd +@item SUM +The sum. +@item MEAN +The arithmetic mean. +@item MAXIMUM +The maximum value. +@item MINIMUM +The minimum value. +@end table + +The following examples assume a dataset which is the results of a survey. +Each respondent has indicated annual income, their sex and city of residence. +One could create a bar chart showing how the mean income varies between of residents of different cities, thus: +@example +GRAPH /BAR = MEAN(@var{income}) BY @var{city}. +@end example + +This can be extended to also indicate how income in each city differs between the sexes. +@example +GRAPH /BAR = MEAN(@var{income}) BY @var{city} BY @var{sex}. +@end example + +One might also want to see how many respondents there are from each city. This can be achieved as follows: +@example +GRAPH /BAR = COUNT BY @var{city}. +@end example + +Bar charts can also be produced using the @ref{FREQUENCIES} and @ref{CROSSTABS} commands. + @node CORRELATIONS @section CORRELATIONS @@ -1647,7 +1715,7 @@ The default is 0.05. @display QUICK CLUSTER @var{var_list} - [/CRITERIA=CLUSTERS(@var{k}) [MXITER(@var{max_iter})]] + [/CRITERIA=CLUSTERS(@var{k}) [MXITER(@var{max_iter})] CONVERGE(@var{epsilon}) [NOINITIAL]] [/MISSING=@{EXCLUDE,INCLUDE@} @{LISTWISE, PAIRWISE@}] [/PRINT=@{INITIAL@} @{CLUSTERS@}] @end display @@ -1659,11 +1727,29 @@ of similar values and you already know the number of clusters. The minimum specification is @samp{QUICK CLUSTER} followed by the names of the variables which contain the cluster data. Normally you will also want to specify @subcmd{/CRITERIA=CLUSTERS(@var{k})} where @var{k} is the -number of clusters. If this is not given, then @var{k} defaults to 2. +number of clusters. If this is not specified, then @var{k} defaults to 2. + +If you use @subcmd{/CRITERIA=NOINITIAL} then a naive algorithm to select +the initial clusters is used. This will provide for faster execution but +less well separated initial clusters and hence possibly an inferior final +result. + + +@cmd{QUICK CLUSTER} uses an iterative algorithm to select the clusters centers. +The subcommand @subcmd{/CRITERIA=MXITER(@var{max_iter})} sets the maximum number of iterations. +During classification, @pspp{} will continue iterating until until @var{max_iter} +iterations have been done or the convergence criterion (see below) is fulfilled. +The default value of @var{max_iter} is 2. + +If however, you specify @subcmd{/CRITERIA=NOUPDATE} then after selecting the initial centers, +no further update to the cluster centers is done. In this case, @var{max_iter}, if specified. +is ignored. -The command uses an iterative algorithm to determine the clusters for -each case. It will continue iterating until convergence, or until @var{max_iter} -iterations have been done. The default value of @var{max_iter} is 2. +The subcommand @subcmd{/CRITERIA=CONVERGE(@var{epsilon})} is used +to set the convergence criterion. The value of convergence criterion is @var{epsilon} +times the minimum distance between the @emph{initial} cluster centers. Iteration stops when +the mean cluster distance between one iteration and the next +is less than the convergence criterion. The default value of @var{epsilon} is zero. The @subcmd{MISSING} subcommand determines the handling of missing variables. If @subcmd{INCLUDE} is set, then user-missing values are considered at their face