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
(3) Group.1 is a ?list? of number
(4) x which is a 844x7 matrix having value "Good", "Moderate", etc.
A few questions:
(A) Is the interpretation given above correct?
(B) Does the .. ..$ : NULL mean that the matrix has no row names?
(C) What does "attr(*, "dimnames")=List of 2" mean?
(D) Does it mean that the dimensions of the matrix are stored as two separate
lists?
(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
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