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5 Command file: Reading the data 58ASReml codeactionscore !SUB -0.5 1.5 2.5 replaces data values of -0.5, 1.5 and 2.5 with 1, 2and 3 respectively; a data value of 1.51 would bereplaced by 0 since it is not in the list or very closeto a number in the listblock 8variety 20yieldplot * !=variety !SEQVar 3Nit 4VxN 12 !=Var !-1 !*4 !+NitYA !V98=YA !NA 0YB !V99=YB !NA 0 !+V98 !D0in the case where– there are multiple units per plot,– contiguous plots have different treatments, and– the records are sorted units within plots withinblocks,this code generates a plot factor assuming a newplot whenever the code in V2 (variety) changes; nofield would be read unless there were later definitionswhich are not created by transformation,assuming Var is coded 1:3 and Nit is coded 1:4, thissyntax could be used to create a new factor VxN withthe 12 levels of the composite Var by Nit factor.will discard records where both YA and YB have missingvalues (assuming neither have zero as valid data).The first line sets the focus to variable 98, copies YAinto V98 and changes any missing values in V98 tozero. The second line sets the focus to variable 99,copies YB into V99 and changes any missing valuesin V99 to zero. It then adds V98 and discards thewhole record if the result is zero, i.e. both YA andYB have missing values for that record. Variables 98and 99 are not labelled and so are not retained forsubsequent use in analysis.Special note on covariatesCovariates are variates that appear as independent variables in the model. It isrecommended that covariates be centred and scaled to have a mean of zero anda variance of approximately one to avoid failure to detect singularities. This canbe achieved either• externally to ASReml in data file preparation,• using !RESCALE -mean scale where mean and scale are user supplied values,for example, age !rescale -200 !/10.