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A2KEEP procedure

Copies information from an A2WAY analysis into Genstat data structures (R.W. Payne).


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


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


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


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


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.





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

Procedures: A2WAY, A2DISPLAY.

Commands for: Analysis of variance.


CAPTION   'A2KEEP example',\
          !t('Data from Snedecor & Cochran (1980), Statistical Methods',\
          '(7th edition), page 216 and also see page 252.');\
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
 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]\
Updated on June 20, 2019

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