I am just curious. Every once and a while I see an attribute attached to an object called "assign". What meaning does this have? For example: dist ~ speed, data=cars forms a matrix like: num [1:50, 1:2] 1 1 1 1 1 1 1 1 1 1 ... - attr(*, "dimnames")=List of 2 ..$ : chr [1:50] "1" "2" "3" "4" ... ..$ : chr [1:2] "(Intercept)" "speed" - attr(*, "assign")= int [1:2] 0 1 The "dimnames" attribute is fairly self-explanatory. I just am not sure what the "assign" attribute means. Thank you. Kevin ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. |
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> I am just curious. Every once and a while I see an attribute attached to an object called "assign". What meaning does this have? For example: > > dist ~ speed, data=cars > > forms a matrix like: > > num [1:50, 1:2] 1 1 1 1 1 1 1 1 1 1 ... > - attr(*, "dimnames")=List of 2 > ..$ : chr [1:50] "1" "2" "3" "4" ... > ..$ : chr [1:2] "(Intercept)" "speed" > - attr(*, "assign")= int [1:2] 0 1 > > The "dimnames" attribute is fairly self-explanatory. I just am not sure what the "assign" attribute means. It has to do with the mapping between terms of the formula and columns of the design matrix: > str(model.matrix(Ozone~factor(Month)+Wind,data=airquality)) num [1:116, 1:6] 1 1 1 1 1 1 1 1 1 1 ... - attr(*, "dimnames")=List of 2 ..$ : chr [1:116] "1" "2" "3" "4" ... ..$ : chr [1:6] "(Intercept)" "factor(Month)6" "factor(Month)7" "factor(Month)8" ... - attr(*, "assign")= int [1:6] 0 1 1 1 1 2 - attr(*, "contrasts")=List of 1 ..$ factor(Month): chr "contr.treatment" I.e. columns 2:5 belong to the first non-intercept term, factor(Month). (Notice that it is implicitly assumed that you have the corresponding terms() output to hand, likewise for the "contrasts" attribute.) -- O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 ~~~~~~~~~~ - ([hidden email]) FAX: (+45) 35327907 ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. |
I am sorry I still don't understand. In the example you give the 'assign' vecotr is a vector of length 6 and there are indeed 6 columns in the data frame. But the formula only has two variables namely 'Month' and 'Wind'. Where do the values if the 'assign' vector come from? I see '0 1 1 1 1 2'. What is '1' an index to? '2'? Maybe I am get confused with what the term 'factors' does to the formula. Thanks agiain for your help. Kevin ---- Peter Dalgaard <[hidden email]> wrote: > [hidden email] wrote: > > I am just curious. Every once and a while I see an attribute attached to an object called "assign". What meaning does this have? For example: > > > > dist ~ speed, data=cars > > > > forms a matrix like: > > > > num [1:50, 1:2] 1 1 1 1 1 1 1 1 1 1 ... > > - attr(*, "dimnames")=List of 2 > > ..$ : chr [1:50] "1" "2" "3" "4" ... > > ..$ : chr [1:2] "(Intercept)" "speed" > > - attr(*, "assign")= int [1:2] 0 1 > > > > The "dimnames" attribute is fairly self-explanatory. I just am not sure what the "assign" attribute means. > > It has to do with the mapping between terms of the formula and columns > of the design matrix: > > > str(model.matrix(Ozone~factor(Month)+Wind,data=airquality)) > num [1:116, 1:6] 1 1 1 1 1 1 1 1 1 1 ... > - attr(*, "dimnames")=List of 2 > ..$ : chr [1:116] "1" "2" "3" "4" ... > ..$ : chr [1:6] "(Intercept)" "factor(Month)6" "factor(Month)7" > "factor(Month)8" ... > - attr(*, "assign")= int [1:6] 0 1 1 1 1 2 > - attr(*, "contrasts")=List of 1 > ..$ factor(Month): chr "contr.treatment" > > I.e. columns 2:5 belong to the first non-intercept term, factor(Month). > (Notice that it is implicitly assumed that you have the corresponding > terms() output to hand, likewise for the "contrasts" attribute.) > -- > O__ ---- Peter Dalgaard Øster Farimagsgade 5, Entr.B > c/ /'_ --- Dept. of Biostatistics PO Box 2099, 1014 Cph. K > (*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918 > ~~~~~~~~~~ - ([hidden email]) FAX: (+45) 35327907 ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. |
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