list(...) I would like to extend zoo objects for use in a hydrological application. By that I mean I want to attach various attributes, such as id numbers, coordinates of the observation location, a units specification, etc. I might also want to add to the "class" attribute (inheriting from "zoo") and define some custom methods. I can add attributes() to a zoo object, but the problem is that when I do operations on the object, such as window, `[`, lag etc, the attributes are lost. That makes it awkward to manage.
E.g. > foo <- zoo(1:5, order.by=as.Date(1:5)) > attr(foo, "location") <- c(150, -35) The functions below all return a modified zoo object; test which ones keep the user-specified attributes: > attr(foo[1:4], "location") NULL > attr(window(foo), "location") NULL > attr(lag(foo), "location") NULL > attr(na.approx(foo), "location") ## this one keeps attributes [1] 150 -35 > attr(rollmean(foo, 1), "location") NULL > attr(aggregate(foo, months, mean), "location") NULL I notice that many operations on ts objects have the same behaviour (dropping user-specified attributes). In contrast, subsetting (indexing) a data.frame keeps them, as I had expected. Any ideas for how to manage this? Felix -- Felix Andrews / 安福立 PhD candidate Integrated Catchment Assessment and Management Centre The Fenner School of Environment and Society The Australian National University (Building 48A), ACT 0200 Beijing Bag, Locked Bag 40, Kingston ACT 2604 http://www.neurofractal.org/felix/ 3358 543D AAC6 22C2 D336 80D9 360B 72DD 3E4C F5D8
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