r - Why does one-row xts object not get a timezone? (why does it ignore/override the default argument) -

frustrated unit test complaining, narrowed down 1 xts object has timezone set "utc", other has set "".

and i've narrowed down further seems creating xts object 1 row, compared 2+ rows:

> str(xts( c(1,2), as.posixct("2015-01-01 00:00:00")+0:1)) ‘xts’ object on 2015-01-01/2015-01-01 00:00:01 containing:   data: num [1:2, 1] 1 2   indexed objects of class: [posixct,posixt] tz: utc   xts attributes:    null  > str(xts( c(1), as.posixct("2015-01-01 00:00:01"))) ‘xts’ object on 2015-01-01 00:00:01/2015-01-01 00:00:01 containing:   data: num [1, 1] 1   indexed objects of class: [posixct,posixt] tz:    xts attributes:    null 

below xts constructor. can see tzone argument gets initialized sys.getenv("tz"), evaluates "utc". i'm confused why tzone ever end "", based on contents of x.

function (x = null, order.by = index(x), frequency = null, unique = true,      tzone = sys.getenv("tz"), ...)  {     if (is.null(x) && missing(order.by))          return(structure(.xts(, 0), index = integer()))     if (!timebased(order.by))          stop("order.by requires appropriate time-based object")     if (inherits(order.by, "dates"))          tzone <- ""     if (inherits(order.by, "date")) {         if (!missing(tzone))              warning(paste(squote("tzone"), "setting ignored date indexes"))         tzone <- "utc"     }     if (nrow(x) > 0 && nrow(x) != length(order.by))          stop("nrow(x) must match length(order.by)")     orderby <- class(order.by)     if (inherits(order.by, "date")) {         order.by <- .posixct(unclass(order.by) * 86400, tz = tzone)     }     if (!isordered(order.by, strictly = !unique)) {         indx <- order(order.by)         if (!is.null(x)) {             if (ncol(x) > 1 || is.matrix(x) || is.data.frame(x)) {                 x <- x[indx, , drop = false]             }             else x <- x[indx]         }         order.by <- order.by[indx]     }     if (!is.null(x) || length(x) != 0) {         x <- as.matrix(x)     }     else x <- numeric(0)     if (orderby == "timedate" && missing(tzone)) {         tzone <- order.by@fincenter     }     else if (!is.null(attr(order.by, "tzone")) && missing(tzone))          tzone <- attr(order.by, "tzone")     if (inherits(order.by, "dates"))          index <- as.numeric(as.posixct(strptime(as.character(order.by),              "(%m/%d/%y %h:%m:%s)")))     else index <- as.numeric(as.posixct(order.by))     x <- structure(.data = x, index = structure(index, tzone = tzone,          tclass = orderby), class = c("xts", "zoo"), .indexclass = orderby,          tclass = orderby, .indextz = tzone, tzone = tzone, ...)     if (!is.null(attributes(x)$dimnames[[1]]))          dimnames(x) <- dimnames(x)     x } 

this has posixct objects losing tzone attribute when add integer sequence them. if create posixct vector using seq, tzone attribute retained. illustrate:

> attributes(as.posixct("2015-01-01")) $class [1] "posixct" "posixt"   $tzone [1] ""  > attributes(as.posixct("2015-01-01")+0) $class [1] "posixct" "posixt"   > attributes(seq(as.posixct("2015-01-01"), by="sec", length.out=1)) $class [1] "posixct" "posixt"   $tzone [1] "" 

i need think bit more whether or not bug in constructor.

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i don't think bug in xts constructor. issue constructor honors tzone attribute if it's present, , sets sys.getenv("tz") default if not. adding integer sequence posixct object removes tzone attribute, that's why see behavior do.

if want specific timezone on index , you're creating via as.posixct, need set tz argument explicitly. example:

> str(xts(1, as.posixct("2015-01-01", tz=sys.getenv("tz")))) ‘xts’ object on 2015-01-01/2015-01-01 containing:   data: num [1, 1] 1   indexed objects of class: [posixct,posixt] tz: utc   xts attributes:    null