It isn't really clear that it can't work. This does work by inserting NA's.
library(zoo) as.ts(as.zoo(lynx)[ c(1:3, 7) ] ) ## Time Series: ## Start = 1821 ## End = 1827 ## Frequency = 1 ## [1] 269 321 585 NA NA NA 3928 On Mon, Jun 10, 2024 at 10:32 AM Martin Maechler <maech...@stat.math.ethz.ch> wrote: > > >>>>> Spencer Graves > >>>>> on Mon, 10 Jun 2024 07:50:13 -0500 writes: > > > Hi, Gabor et al.: Thanks for this. I should change my > > current application to use either zoo or xts, as Gabor > > suggests. > > > > However, I was surprised to learn that "[.ts" does NOT > > return an object of class "ts". I see that "head.default" > > and "head.matrix" both call "[", so "head" cannot return a > > ts object, because "[" doesn't. > > Yes, the default head() and tail() are built on `[` very much > on purpose. > Note that `[` should *not* keep the "ts" property in > general, e.g., > lynx[c(1:3, 7)] > cannot be a regular time series > > I think I'd consider using windows() for a head.ts() and tail.ts(), > but in any case, I am sympathetic adding such methods to "base R"'s > utils package. > > > Martin > > > Best Wishes, Spencer Graves > > > > On 6/9/24 8:40 PM, Gabor Grothendieck wrote: > >> zoo overcomes many of the limitations of ts: > >> > >> library(zoo) as.ts(head(as.zoo(presidents))) ## Qtr1 Qtr2 > >> Qtr3 Qtr4 ## 1945 NA 87 82 75 ## 1946 63 50 > >> > >> xts also works here. > >> > >> On Sun, Jun 9, 2024 at 12:04 PM Spencer Graves > >> <spencer.gra...@prodsyse.com> wrote: > >>> > >>> Hello, All: > >>> > >>> > >>> The 'head' and 'tail' functions strip the time from a > >>> 'ts' object. Example: > >>> > >>> > >>> > head(presidents) [1] NA 87 82 75 63 50 > >>> > >>> > >>> > window(presidents, 1945, 1946.25) Qtr1 Qtr2 Qtr3 Qtr4 > >>> 1945 NA 87 82 75 1946 63 50 > >>> > >>> > >>> Below please find code for 'head.ts' and 'tail.ts' that > >>> matches 'window'. > >>> > >>> > >>> Comments? Spencer Graves > >>> > >>> head.ts <- function(x, n=6L, ...){ tmx <- > >>> as.numeric(time(x)) > >>> # > >>> utils:::checkHT(n, d <- dim(x)) if(is.na(n[1]) || > >>> n[1]==0)ts(NULL) > >>> # > >>> firstn <- head(tmx, n[1]) if(is.null(d)){ > >>> return(window(x, firstn[1], tail(firstn, 1))) } else{ > >>> if(length(n)<2){ return(window(x, firstn[1], > >>> tail(firstn, 1))) } else { Cols <- head(1:d[2], n[2]) > >>> xn2 <- x[, Cols[1]:tail(Cols, 1)] return(window(xn2, > >>> firstn[1], tail(firstn, 1))) } } } > >>> > >>> > >>> tail.ts <- function (x, n = 6L, ...) { > >>> utils:::checkHT(n, d <- dim(x)) tmx <- > >>> as.numeric(time(x)) > >>> # > >>> if(is.na(n[1]) || n[1]==0)ts(NULL) > >>> # > >>> lastn <- tail(tmx, n[1]) if(is.null(d)){ > >>> return(window(x, lastn[1], tail(lastn, 1))) } else{ > >>> if(length(n)<2){ return(window(x, lastn[1], tail(lastn, > >>> 1))) } else { Cols <- head(1:d[2], n[2]) xn2 <- x[, > >>> Cols[1]:tail(Cols, 1)] return(window(xn2, lastn[1], > >>> tail(lastn, 1))) } } } > >>> > >>> > >>> # examples head(presidents) > >>> > >>> head(presidents, 2) > >>> > >>> npresObs <- length(presidents) head(presidents, > >>> 6-npresObs) > >>> > >>> try(head(presidents, 1:2)) # 'try-error' > >>> > >>> try(head(presidents, 0)) # 'try-error' > >>> > >>> # matrix time series str(pres <- > >>> cbind(n=1:length(presidents), presidents)) head(pres, 2) > >>> > >>> head(pres, 2-npresObs) > >>> > >>> head(pres, 1:2) head(pres, 2:1) head(pres, 1:3) > >>> > >>> # examples tail(presidents) > >>> > >>> tail(presidents, 2) > >>> > >>> npresObs <- length(presidents) tail(presidents, > >>> 6-npresObs) > >>> > >>> try(tail(presidents, 1:2)) # 'try-error' > >>> > >>> try(tail(presidents, 0)) # 'try-error' > >>> > >>> # matrix time series str(pres <- > >>> cbind(n=1:length(presidents), presidents)) tail(pres, 2) > >>> > >>> tail(pres, 2-npresObs) > >>> > >>> tail(pres, 1:2) tail(pres, 2:1) tail(pres, 1:3) > >>> > >>> # for unit testing: headPres <- head(presidents) pres6 > >>> <- ts(presidents[1:6], time(presidents)[1], > >>> frequency=frequency(presidents)) > >>> stopifnot(all.equal(headPres, pres6)) > >>> > >>> headPres2 <- head(presidents, 2) pres2 <- > >>> ts(presidents[1:2], time(presidents)[1], > >>> frequency=frequency(presidents)) > >>> stopifnot(all.equal(headPres2, pres2)) > >>> > >>> npresObs <- length(presidents) headPres. <- > >>> head(presidents, 6-npresObs) > >>> stopifnot(all.equal(headPres., pres6)) > >>> > >>> headPresOops <- try(head(presidents, 1:2)) > >>> stopifnot(class(headPresOops) == 'try-error') > >>> > >>> headPres0 <- try(head(presidents, 0)) > >>> stopifnot(class(headPres0) == 'try-error') > >>> > >>> str(pres <- cbind(n=1:length(presidents), presidents)) > >>> headP2 <- head(pres, 2) > >>> > >>> p2 <- ts(pres[1:2, ], time(presidents)[1], > >>> frequency=frequency(presidents)) > >>> stopifnot(all.equal(headP2, p2)) > >>> > >>> headP2. <- head(pres, 2-npresObs) > >>> stopifnot(all.equal(headP2., p2)) > >>> > >>> > >>> ############# > >>> > >>> > >>> sessionInfo() R version 4.4.0 (2024-04-24) Platform: > >>> aarch64-apple-darwin20 Running under: macOS Sonoma 14.5 > >>> > >>> Matrix products: default BLAS: > >>> > /System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib > >>> > >>> LAPACK: > >>> > /Library/Frameworks/R.framework/Versions/4.4-arm64/Resources/lib/libRlapack.dylib; > >>> LAPACK version 3.12.0 > >>> > >>> locale: [1] > >>> en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8 > >>> > >>> time zone: America/Chicago tzcode source: internal > >>> > >>> attached base packages: [1] stats graphics grDevices > >>> utils datasets [6] methods base > >>> > >>> loaded via a namespace (and not attached): [1] > >>> compiler_4.4.0 tools_4.4.0 > >>> > >>> ______________________________________________ > >>> R-devel@r-project.org mailing list > >>> https://stat.ethz.ch/mailman/listinfo/r-devel > >> > >> > >> > > > ______________________________________________ > > R-devel@r-project.org mailing list > > https://stat.ethz.ch/mailman/listinfo/r-devel -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel