Re: [R] cumsum on chron objects
On 5/17/05, Sebastian Luque <[EMAIL PROTECTED]> wrote: > Hello Gabor, > > Thanks for your reply. na.locf would replace the NA's with the most recent > non-NA, so it wouldn't create a sequence of chron dates/times (via > as.vector, as in your example). To expand my original example: > > > >> On 5/17/05, Sebastian Luque <[EMAIL PROTECTED]> wrote: > > [...] > > >>> DateTime > >>> 13/10/03 12:30:35 > >>> NA > >>> NA > >>> NA > >>> 15/10/03 16:30:05 > >>> NA > >>> NA > >>> ... > > I thought one could replace the NA's by the desired interval, say 1 day, > so if the above chron object was named nachron, one could do: > > nachron[is.na(nachron)] <- 1 > > and, for simplicity, applying on each "block" separately: > > cumsum(nachron) > > would give: > > DateTime > 13/10/03 12:30:35 > 14/10/03 12:30:35 > 15/10/03 12:30:35 > 16/10/03 12:30:35 > > for the first "block", and: > > DateTime > 15/10/03 16:30:05 > 16/10/03 16:30:05 > 17/10/03 16:30:05 > ... > > for the second one. Since there are not too many blocks I may end up doing > it in Excel, but it would be nice to know how to do it in R! I did not understand that you wanted a sequence. If x and x.locf are as in the previous response then: my.seq <- function(x) seq(from = x[1], len = length(x)) chron(unlist(tapply(x, x.locf, my.seq))) or if you want to use cumsum: xx <- as.vector(x); xx[is.na(xx)] <- 1 chron(unlist(tapply(xx, x.locf, cumsum))) __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] cumsum on chron objects
Hello Gabor, Thanks for your reply. na.locf would replace the NA's with the most recent non-NA, so it wouldn't create a sequence of chron dates/times (via as.vector, as in your example). To expand my original example: >> On 5/17/05, Sebastian Luque <[EMAIL PROTECTED]> wrote: [...] >>> DateTime >>> 13/10/03 12:30:35 >>> NA >>> NA >>> NA >>> 15/10/03 16:30:05 >>> NA >>> NA >>> ... I thought one could replace the NA's by the desired interval, say 1 day, so if the above chron object was named nachron, one could do: nachron[is.na(nachron)] <- 1 and, for simplicity, applying on each "block" separately: cumsum(nachron) would give: DateTime 13/10/03 12:30:35 14/10/03 12:30:35 15/10/03 12:30:35 16/10/03 12:30:35 for the first "block", and: DateTime 15/10/03 16:30:05 16/10/03 16:30:05 17/10/03 16:30:05 ... for the second one. Since there are not too many blocks I may end up doing it in Excel, but it would be nice to know how to do it in R! Cheers and thank you, -- Sebastian P. Luque __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] cumsum on chron objects
On 5/17/05, Sebastian Luque <[EMAIL PROTECTED]> wrote: > Hi, > > Is there some alternative to cumsum for chron objects? I have data frames > that contain some chron objects that look like this: > > DateTime > 13/10/03 12:30:35 > NA > NA > NA > 15/10/03 16:30:05 > NA > NA > ... > > and I've been trying to replace the NA's so that a date/time sequence is > created starting with the preceding available value. Because the number of > rows with NA's following each available date/time is unknown, I've split > the data frame using: > > splitdf <- split(df, as.factor(df$DateTime)) > > so that I can later use lapply to work on each "block" of data. I thought > I could use cumsum and set the NA's to the desired interval to create the > date/time sequence starting with the first row. However, this function is > not defined for chron objects. Does anybody know of alternatives to create > such a sequence? > The 'zoo' package has na.locf which stands for Last Occurrence Carried Forward, which is what I believe you want. First let us create some test data, x: > library(chron); library(zoo) > x <- chron(c(1.5, 2, NA, NA, 4, NA)) > x [1] (01/02/70 12:00:00) (01/03/70 00:00:00) (NA NA) [4] (NA NA) (01/05/70 00:00:00) (NA NA) > # na.locf is intended for zoo objects but we can convert > # the chron object to zoo, apply na.locf and convert back: > chron(as.vector(na.locf(zoo(as.vector(x) [1] (01/02/70 12:00:00) (01/03/70 00:00:00) (01/03/70 00:00:00) [4] (01/03/70 00:00:00) (01/05/70 00:00:00) (01/05/70 00:00:00) __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
Re: [R] cumsum on chron objects
On 5/17/05, Gabor Grothendieck <[EMAIL PROTECTED]> wrote: > On 5/17/05, Sebastian Luque <[EMAIL PROTECTED]> wrote: > > Hi, > > > > Is there some alternative to cumsum for chron objects? I have data frames > > that contain some chron objects that look like this: > > > > DateTime > > 13/10/03 12:30:35 > > NA > > NA > > NA > > 15/10/03 16:30:05 > > NA > > NA > > ... > > > > and I've been trying to replace the NA's so that a date/time sequence is > > created starting with the preceding available value. Because the number of > > rows with NA's following each available date/time is unknown, I've split > > the data frame using: > > > > splitdf <- split(df, as.factor(df$DateTime)) > > > > so that I can later use lapply to work on each "block" of data. I thought > > I could use cumsum and set the NA's to the desired interval to create the > > date/time sequence starting with the first row. However, this function is > > not defined for chron objects. Does anybody know of alternatives to create > > such a sequence? > > > > The 'zoo' package has na.locf which stands for Last Occurrence Carried > Forward, which is what I believe you want. > > First let us create some test data, x: > > > library(chron); library(zoo) > > x <- chron(c(1.5, 2, NA, NA, 4, NA)) > > x > [1] (01/02/70 12:00:00) (01/03/70 00:00:00) (NA NA) > [4] (NA NA) (01/05/70 00:00:00) (NA NA) > > > # na.locf is intended for zoo objects but we can convert > > # the chron object to zoo, apply na.locf and convert back: > > > chron(as.vector(na.locf(zoo(as.vector(x) > [1] (01/02/70 12:00:00) (01/03/70 00:00:00) (01/03/70 00:00:00) > [4] (01/03/70 00:00:00) (01/05/70 00:00:00) (01/05/70 00:00:00) > Just to reply to my own post, it can actually be done even more simply: chron(na.locf(as.vector(x))) Also in re-reading my post, I think the O in locf stands for observation rather than occurrence. __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
[R] cumsum on chron objects
Hi, Is there some alternative to cumsum for chron objects? I have data frames that contain some chron objects that look like this: DateTime 13/10/03 12:30:35 NA NA NA 15/10/03 16:30:05 NA NA ... and I've been trying to replace the NA's so that a date/time sequence is created starting with the preceding available value. Because the number of rows with NA's following each available date/time is unknown, I've split the data frame using: splitdf <- split(df, as.factor(df$DateTime)) so that I can later use lapply to work on each "block" of data. I thought I could use cumsum and set the NA's to the desired interval to create the date/time sequence starting with the first row. However, this function is not defined for chron objects. Does anybody know of alternatives to create such a sequence? Thanks in advance, -- Sebastian P. Luque __ R-help@stat.math.ethz.ch mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
