DREPMEASURES procedure

Plots profiles and differences of profiles for repeated measures data (J.T.N.M. Thissen).


Options

TITLE = text
Title for the plots; default *

GROUPS = factors
List of one or two factors; one factor gives one plot while a list with two factors gives as many plots as the number of levels of the first factor in the list; must be set

TIMEPOINTS = variate
Variate of timepoints; by default the suffixes of the DATA pointer are used

DIFFERENCES = string
Can suppress plotting of the differences (no, yes); default no


Parameter

DATA = pointers
Each pointer contains the data variates (observed at successive times)

GROUPMEANS = tables
To save the calculated treatment means at each timepoint


Description

A repeated measures experiment is one in which the same set of units, or subjects, is observed at a sequence of times to investigate treatment effects over a period of time.

   DREPMEASURES produces high-resolution graphs of the progress in time for the data variates specified in a pointer by the DATA parameter. Each variate contains the measurements made on the set of units at one of the occasions on which they were observed. The timepoints along the x-axes of the graph are the suffixes of the pointer unless the option TIMEPOINTS is specified. The grouping of the subjects should be specified by one or two factors, and input using the GROUPS option. If one factor is specified, the means of the observations at each level of the factor are plotted in one graph. If two factors are specified several graphs are produced: each graph is a plot of the means of the observations at the various levels of the second factor for a particular level of the first.

   The means are calculated with the directive TABULATE. If the data variates contain missing values a warning is printed indicating the possibility of misleading results. (Before using DREPMEASURES the missing values can be estimated using the procedures ANTMVESTIMATE or MULTMISSING.)

   If option DIFFERENCES=yes, two plots are produced, beside each other: one of the profiles and one of the differences with the first level. The default setting no gives the plot of the profiles only. Plots of differences can be produced only if the factor has more than one level. The TITLE option can be used to provide a title for the plots.

   The calculated means can be saved by specifying parameter GROUPMEANS.


Options: TITLE, GROUPS, TIMEPOINTS, DIFFERENCES.

Parameters: DATA, GROUPMEANS.


Method

Means are calculated with the directive TABULATE. If restricted variates are specified in DATA, procedure SUBSET is used to remove any levels of the factors that are not present in the subset of subjects.


Action with RESTRICT

If any of the variates in the DATA pointer is restricted, only the units not excluded by the restriction will be used for the graphs. If any other DATA variate or GROUPS factor is restricted, it must be restricted to the same set of units. The variate specified by TIMEPOINTS must not be restricted.