Copies information from an A2WAY analysis into Genstat data structures (R.W. Payne).
Options
FACTORIAL = scalar |
Sets a limit on the number of factors in the terms formed from the TERMS formula; default 2 |
|---|---|
RESIDUALS = variate |
Saves the residuals |
FITTEDVALUES = variate |
Saves the fitted values |
COMBINATIONS = string token |
Factor combinations for which to form predicted means (present, estimable); default esti |
ADJUSTMENT = string token |
Type of adjustment to be made when predicting means (marginal, equal, observed); default marg |
LSDLEVEL = scalar |
Significance level (%) for least significant differences; default 5 |
AOVTABLE = pointer |
To save the analysis-of-variance table as a pointer with a variate or text for each column (source, d.f., s.s., m.s. etc) |
RMETHOD = string token |
Type of residuals to form if the RESIDUALS option is set (simple, standardized); default simp |
EXIT = scalar |
Saves an exit code indicating the properties of the design |
SAVE = pointer |
Save structure (from A2WAY) for the analysis; if omitted, output is from the most recent A2WAY analysis |
Parameters
TERMS = formula |
Specifies the treatment terms whose means &c are to be saved |
|---|---|
MEANS = table or pointer to tables |
Saves tables of means for the terms or pointer to tables |
SEMEANS = table or pointer to tables |
Saves approximate effective standard errors of means |
SEDMEANS = table or pointer to tables |
Saves standard errors of differences between means |
LSD = table or pointer to tables |
Saves least significant differences |
Description
The procedure A2WAY provides specialized facilities for analysis of variance with either one or two treatment factors. There can also be a blocking factor. It automatically determines the type of design and uses the appropriate method: the ANOVA directive if the design is balanced, or the regression directives (FIT, ADD and so on) if it is unbalanced.
Procedure A2KEEP allows you to copy information from the analysis into Genstat data structures. By default the information is from the most recent analysis performed by A2WAY. Alternatively, you can set the SAVE option to a save structure (saved using the SAVE parameter of A2WAY) to save information from an earlier analysis.
You can use the parameters of A2KEEP to save means, standard errors and least significant differences for the treatment main effects and interactions. The TERMS parameter should be set to a model formula to define the main effects and interactions whose means &c you want to save. The MEANS parameter can then save tables of means. The SEMEANS parameter saves their standard errors (also in a table). The SEDMEANS parameter saves standard errors for differences between the means (in a symmetric matrix), and the LSD parameter saves least significant differences (also in a symmetric matrix). The significance level for the least significant differences can be change from the default of 5% using the LSDLEVEL option. If you have a single term, you can supply a table or symmetric matrix for each of these parameters, as appropriate. However, if you have several terms, you must supply a pointer which will then be set up to contain as many tables or symmetric matrices as there are terms. The LSDLEVEL option sets the significance level (as a percentage) for the least significant differences.
The FACTORIAL option sets a limit in the number of factors in the terms generated from the TERMS model formula. So
A2KEEP [FACTORIAL=1] A*B; MEANS=MA,MB
would save only the main effects of A and B. The option is provided for compatibility with the AKEEP directive. However, an alternative (and simpler) way of saving means only for the main effects would be to put
A2KEEP [FACTORIAL=1] A+B; MEANS=MA,MB
The default for FACTORIAL is 2.
For unbalanced designs (analysed by A2WAY using Genstat regression) the means are produced using the PREDICT directive. The first step (A) of the calculation forms the full table of predictions, classified by all the treatment and blocking factors. The second step (B) averages the full table over the factors that do not occur in the table of means. The COMBINATIONS option specifies which cells of the full table are to be formed in Step A. The default setting, estimable, fills in all the cells other than those that involve parameters that cannot be estimated. Alternatively, setting COMBINATIONS=present excludes the cells for factor combinations that do not occur in the data. The ADJUSTMENT option then defines how the averaging is done in Step B. The default setting, marginal, forms a table of marginal weights for each factor, containing the proportion of observations with each of its levels; the full table of weights is then formed from the product of the marginal tables. The setting equal weights all the combinations equally. Finally, the setting observed uses the WEIGHTS option of PREDICT to weight each factor combination according to its own individual replication in the data.
The RESIDUALS option can save the residuals from the analysis, and the FITTEDVALUES option can save the fitted values. The RMETHOD option controls whether simple or standardized residuals are saved; by default RMETHOD=simple. The AOVTABLE option saves the analysis-of-variance table, as a pointer with a variate or a text for each column of the table. The pointer elements are labelled with the column labels of the table, and the variates contain missing values where the table has blanks. These can be printed as blanks by setting option MISSING=' ' in the PRINT directive.
The EXIT option can save an exit code indicating how the analysis was done. For the exact meanings of the values see the ANOVA directive. Essentially, it has the values 0 or 1 if the analysis has been done using ANOVA (0 if design orthogonal and 1 if it is balanced). Other values indicate that it has been done using the regression directives.
Options: FACTORIAL, RESIDUALS, FITTEDVALUES, COMBINATIONS, ADJUSTMENT, LSDLEVEL, AOVTABLE, RMETHOD, EXIT, SAVE.
Parameters: TERMS, MEANS, SEMEANS, SEDMEANS, LSD.
Method
Action with RESTRICT
If the Y variate in A2WAY was restricted, only the units not excluded by the restriction will have been analysed.
See also
Commands for: Analysis of variance.
Example
CAPTION 'A2KEEP example',\
!t('Data from Snedecor & Cochran (1980), Statistical Methods',\
'(7th edition), page 216 and also see page 252.');\
STYLE=meta,plain
FACTOR [LEVELS=4; VALUES=(1...4)6] Fat
VARIATE [VALUES=64,78,75,55, 72,91,93,66, 68,97,78,49,\
77,82,71,64, 56,85,63,70, 95,77,76,68] Absorbed
A2WAY [PRINT=aovtable,means; TREATMENTS=Fat; FPROBABILITY=yes;\
PLOT=*] Absorbed
A2KEEP Fat; MEANS=FatMeans; SED=FatSED
PRINT FatMeans,FatSED
CAPTION !t('Data from Snedecor & Cochran (1980), Statistical Methods',\
'(7th edition), page 305.')
FACTOR [LABELS=!T(Beef,Cereal,Pork); VALUES=(1...3)20] Source
FACTOR [LABELS=!T(High,Low); VALUES=3(1,2)10] Amount
VARIATE [NVALUES=60] Gain
READ Gain
73 98 94 90 107 49
102 74 79 76 95 82
118 56 96 90 97 73
104 111 98 64 80 86
81 95 102 86 98 81
107 88 102 51 74 97
100 82 108 72 74 106
87 77 91 90 67 70
117 86 120 95 89 61
111 92 105 78 58 82 :
A2WAY [PRINT=aovtable,means; TREATMENTS=Source,Amount; FPROBABILITY=yes;\
PLOT=*] Gain
A2KEEP Source*Amount; MEANS=!p(Sm,Am,SAm); SED=!p(Ssed,Ased,SAsed)
PRINT [RLPRINT=integers,labels,identifiers; CLPRINT=integers,identifiers]\
Sm,Ssed,Am,Ased,SAm,SAsed