I'll answer your question inline. On 2025-01-24 2:03 p.m., Sorkin, John wrote:
I ran the following code: marginalcats <- aggregate(meanbyCensusIDAndDay3$cats, list(meanbyCensusIDAndDay3$CensusID),table) followed by str(marginalcats)I received the following output: 'data.frame': 844 obs. of 2 variables: $ Group.1: num 6e+09 6e+09 6e+09 6e+09 6e+09 ... $ x : int [1:844, 1:7] 14 14 14 14 14 14 14 14 14 14 ... ..- attr(*, "dimnames")=List of 2 .. ..$ : NULL .. ..$ : chr [1:7] "Good" "Moderate" "Unhealthy For Some" "Unhealthy" ... I am trying to understand the output. I believe it says that marginalcats (1) is a data frame (2) the df has two elements (I) Group.1 and (II) x
Correct so far.
(3) Group.1 is a ?list? of number
No, it's a numeric vector. The length doesn't print because it's in a dataframe, so the length is 844, the number of dataframe observations.
(4) x which is a 844x7 matrix having value "Good", "Moderate", etc.
Correct.
A few questions: (A) Is the interpretation given above correct? (B) Does the .. ..$ : NULL mean that the matrix has no row names?
Yes.
(C) What does "attr(*, "dimnames")=List of 2" mean?
That says x has an attribute called "dimnames", which is a list with two elements. They are the row names (which is NULL, you don't have any) and the column names.
(D) Does it mean that the dimensions of the matrix are stored as two separate lists?
No. The dim is an attribute which is shown implicitly as "[1:844, 1:7]", i.e. c(844, 7).
Duncan Murdoch
(E) If so, how do I access the lists? When I enter dimnames(marginalcatsx$x) I receive: [[1]] NULL [[2]] [1] "Good" "Moderate" "Unhealthy For Some" "Unhealthy" "Very Unhealthy" "Hazardous1" [7] "Hazardous2" Thank you, John John David Sorkin M.D., Ph.D. Professor of Medicine, University of Maryland School of Medicine; Associate Director for Biostatistics and Informatics, Baltimore VA Medical Center Geriatrics Research, Education, and Clinical Center; PI Biostatistics and Informatics Core, University of Maryland School of Medicine Claude D. Pepper Older Americans Independence Center; Senior Statistician University of Maryland Center for Vascular Research; Division of Gerontology and Paliative Care, 10 North Greene Street GRECC (BT/18/GR) Baltimore, MD 21201-1524 Cell phone 443-418-5382 ______________________________________________ [email protected] mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide https://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
______________________________________________ [email protected] mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide https://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
