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newbie question on str output
3 messages · Laura Smith, David Winsemius, Dieter Menne
On Dec 16, 2010, at 11:10 PM, Laura Smith wrote:
Hi! Here is some output from an str command:
str(CO2)
Classes ?nfnGroupedData?, ?nfGroupedData?, ?groupedData? and 'data.frame': 84 obs. of 5 variables: $ Plant : Ord.factor w/ 12 levels "Qn1"<"Qn2"<"Qn3"<..: 1 1 1 1 1 1 1 2 2 2 ... $ Type : Factor w/ 2 levels "Quebec","Mississippi": 1 1 1 1 1 1 1 1 1 1 ... $ Treatment: Factor w/ 2 levels "nonchilled","chilled": 1 1 1 1 1 1 1 1 1 1 ... $ conc : num 95 175 250 350 500 675 1000 95 175 250 ... $ uptake : num 16 30.4 34.8 37.2 35.3 39.2 39.7 13.6 27.3 37.1 ... - attr(*, "formula")=Class 'formula' length 3 uptake ~ conc | Plant .. ..- attr(*, ".Environment")=<environment: R_EmptyEnv> - attr(*, "outer")=Class 'formula' length 2 ~Treatment * Type .. ..- attr(*, ".Environment")=<environment: R_EmptyEnv> - attr(*, "labels")=List of 2 ..$ x: chr "Ambient carbon dioxide concentration" ..$ y: chr "CO2 uptake rate" - attr(*, "units")=List of 2 ..$ x: chr "(uL/L)" ..$ y: chr "(umol/m^2 s)"
What do the nfnGroupdata, nfGroupdata mean, please? Also, what do the attr with formula and outer mean, please?
Per its help page: help(CO2, package=datasets) ... the answer is probably in Pinheiro, J. C. and Bates, D. M. (2000) Mixed-effects Models in S and S-PLUS, Springer. Some datasets and packages are really support material for textbooks, and this appears to be one such case.
How would I find those things out without posting to the list.
Read the help page? Do this: ??CO2
David Winsemius, MD West Hartford, CT
Laura Smith wrote:
What do the nfnGroupdata, nfGroupdata mean, please?
??nfnGroupedData (not nfnGroupdata) gives some information, and tells you, that it is related to package nlme. This package is one of the most useful and has a good documenting book (Pinheiro/Bates), but the groupedData concept is more confusing than helpful. I only started to understand lme and friend until I had noted that it works without grouped data. So better consider CO2 a simple data frame of example data, with historical decoration. I suggest you start with CO2 <- as.data.frame(CO2) Dieter
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