It's likely a trivial question, but I'm attempting to break date and time into their own variables on a GPS data frame containing 1.4 million rows. The timestamp fromat is:
2015-11-19T03:27:56
I've been able to extract the date without any trouble, but the 'T' is giving trouble when attempting to extract time. The following code:
sater001$utc_d <- as.Date(sater001$utc_time_stamp)
where 'sater001$utc_d' is my data frame, and 'utc_time_stamp' is the variable I wish to split, the date is extracted just fine.
But running:
sater001$utc_t <- format(as.POSIXlt(sater001$utc_time_stamp) ,format = "T%H:%M:%S")
Gives me a column filled with T00:00:00 values.
What am I missing here?
We need to also include the T in the format
v2 <- as.POSIXct(v1, format = '%Y-%m-%dT%H:%M:%S')
v2
#[1] "2015-11-19 03:27:56 IST"
Now, we can extract the hms portion
format(v2, "%H:%M:%S")
NOTE: We don't need any additional packages to get the expected result.
data
v1 <- "2015-11-19T03:27:56"
Related
Well, first things first, I'm still a noob and am learning R. I've a a dataset with 0.9 million rows and 36 columns. Of these columns, a column, let's say DATE has dates in string format and an other column, let's say TZ has timezones as strings too.
What I'm trying to do is contract these two columns into one with type POSIXlt date, which has date, time, timezone. Here's my code for trying to get a vector of all the converted dates:
# Let's suppose my data exist in a variable "data" with dates in "DATE" column and timezones in "TZ"
indices <- NULL
dates <- NULL
zones <- unique (data$TZ)
for(i in seq_along(zones)){
indices <<- which(data$TZ==zones[i])
dates <<- c(dates, as.POSIXlt(data$DATE[indices], format = "%m/%d/%Y %H:%M:%S", tz = zones[i]))
}
Now, although there are ~1 million observations, it seems to do the job in 3-4 seconds. Only, that it "seems" to. The result I get is a list with NAs.
It does work when I try to convert a group individually, i.e., store result for every iteration in a different variable, or not run a for loop and do each iteration manually, storing each result in a different variable and, in the end, concatenate it all using c() function.
What am I doing wrong?
For anyone who might stumble here, I figured it.
You can't use c() on a POSIXlt object as it'll convert it into local timezone. (Not the reason for NAs but it's helpful.)
POSIXlt is stored as a list of different variables like mday, zone etc, due to which it's value cannot be used in a data frame element. Instead of POSIXlt, we can use POSIXct as that's internally represented as seconds from 1970-01-01.
Since we'll be replacing a data frame column with dates it's easier to do so with converting it into a tibble using dplyr::as_tibble() and then use dplyr::rbind() to combine the different results.
The reason of NAs being introduced is the lexical scoping in R. I used dates <<- c(dates, as.POSIXlt(data$DATE[indices], format = "%m/%d/%Y %H:%M:%S", tz = zones[i])) due to which, the value of i in zones[i] was NA or unknown.
So, the correct working code is -
dates <- NULL
for (i in seq_along(zones)) {
indices <- which(data$TZ==zones[i])
dts <- as.POSIXct(data$BGN_DATE[indices], format = "%m/%d/%Y %H%M", tz = zones[i])
dates <<- rbind(dates,as_tibble(dts))
}
#Further, to combine the dates into data frame
data <- arrange(data, TZ) %>% mutate(DATEandTime = dates$value) %>% select(-c("DATE","TZ"))
I'm trying to create dataframe in R with a date column that is populated from a pre-defined variable. When I do this the date is changed to a seemingly random future date. Here is what I have:
DateVar <- as.Date("2/6/2020", format = "%m/%d/%Y")
Size <- 50
Results <- data.frame(COMP_NAM=character(Size),
COMM_DTE=as.Date(Size, origin = DateVar),
ID=character(Size),
stringsAsFactors=FALSE)
Then when I look at the dataframe, column COMM_DTE is populated with "2020-04-29". But when I print DateVar R returns "2020-02-06".
Does anyone know why this is happening and how to fix it? Thank you!
everyone!
As part of my clinical study I created a xlsx spreadsheet containing a data set. Only columns 2 to 12 and lines 1 to 307 are useful to me. I now manipulate my spreadsheet under R, after importing it (read_excel, etc.).
In my columns 11 and 12 ('data' and 'raw_data'), some cells correspond to dates (for example the first 2 rows of 'data' and 'raw_data'). Indeed, this corresponds to the patient's visit dates. However, as you can see, these dates are given to me in number of days since the origin "1899-12-30". However, I would like to be able to transform them into a current date format (2019-07-05).
My problem is that in these columns I don't only have dates, I have different numerical results (times, means, scores, etc.) .
I started by transforming the class of my columns from character to factor/numeric so that I could better manipulate the columns later. But I can't change only the format of cells corresponding to a date.
Do you know if it is possible to transform only the cells concerned and if so how?
I attach my code and a preview of my data frame.
Part "Unsuccessful trial": I tried with this kind of thing. Of course the date changes format here but as soon as I try to make this change in the data frame it doesn't work.
Thank you for your help!
# Indicate the id of the patient
id = "01_AA"
# Get protocol data of patient
idlst <- dir("/data/protocolData", full.names = T, pattern = id)
# Convert the xlsx database into dataframe
idData <- data.table::rbindlist(lapply(
idlst,
read_excel,
n_max = 307,
range = cell_cols("B:M"), # just keep the table
), fill = TRUE)
idData <- as.tibble(idData)
idData<- idData %>%
mutate_at(vars(1:10), as.factor)%>%
mutate_at(vars(11:length(idData)), as.numeric)
# Unsuccessful trial
as.Date.character(data[1:2,11:12], origin ='1899-12-30')
Thank you for your comments and indeed this is one of the problems with R.
I solved my problem with the following code where idData is my df.
# Change the data format of the date cells of the column Data and Raw_data:
idData$Data[grepl("date",idData$Measure)] <- as.character(as.Date(
as.numeric(
idData$Data[grepl("date",idData$Measure)]),
origin = "1899-12-30"))
I am a newbie to Stackoverflow, stats and R, so apologies for the simple nature of my question/request for advice:
I am completing analysis of a large data-set comprising of 2 files: a txt containing internal temperature data and a second SPSS data file.
To kick off, I have exported the SPSS data into CSV format and stripped back to contain just the few columns i think i need - house type and occupant type. I have imported all the temperature data and merged the two using a common identifier.
So now I have a merged data frame, containing all the data i need (to begin with) to start completing some analysis.
First question: I have year, date and time as separate columns. However the time column has imported with an incorrect date before "30/12/1899". How can i delete the date part of all observations from this column, but retain the time?
Second question Similar to above, the date colum shows the correct date, but has the time following, which is not correct (every observation showing 00:00:00), how can I delete all the times from this column?
Third question How can I combine the correct Time with correct date, to end up with DD/MM/YYYY HH:MM:SS
Fourth question Should i create subsets of merged to facilitate the analysis: ie: each house type (seperate subsets) vs temp, time and occupant type?
Dates can be brought in as they are instead of factor via the parameter as.is = TRUE i.e.
data <- read.csv(choose.files(), as.is = T)
I would try reading the csv file again and then working with the date time. It will come in as a chron or some format like that and you'll need to change it to Posixct, well I do anyway. To view help on a function, type question mark followed by function name i.e. ?as.posixct.
Date.Time: chron "2018/08/04 10:10:00", ... # '%Y-%m-%d %H:%M:%S' current format as read in from my system.
# Date format you want is '%d/%m/%Y %H:%M'
# tz='' is an empty time zone can't remember exactly you probably should read up on
# finally on the left side of the assign <- I am creating a new column Date.
# You can over write the old column, Date.Time, but can't hurt to learn how to delete
# a column.
data$Date <- as.POSIXct(date$Date.Time, tz='', '%d/%m/%Y %H:%M:%S')
# Now remove the original column. -Date.Time take out Date.Time, if you leave the
# minus out, the data will contain the subset Date.Time and no other columns.
data <- subset(data, select = -Date.Time)
Try this first, and I will look into removing time with in a date field. I have an idea, but I'd rather see if this helps with the problem first.
Though if you do want to merge the Year, month, day columns, you could try something like this, seem like a logical thing to do, you can always keep the original format and delete it later. It's not hurting anything.
data$YMD <- paste(data$Year," ",
data$Month, " ",
data$Day)
Also while you are at it. Install a library called dplyr, written by the same guy that did ggplot2, Hadley....
install.packages("dplyr")
# The add it to the top of your file like ggplot.
library(dplyr)
I have run into an issue I do not understand, and I have not been able to find an answer to this issue on this website (I keep running into answers about how to convert dates to numeric or vice versa, but that is exactly what I do not want to know).
The issue is that R converts values that are formatted as a date (for instance "20-09-1992") to numeric values when you assign them to a matrix or data frame.
For example, we have "20-09-1992" with a date format, we have checked this using class().
as.Date("20-09-1992", format = "%d-%m-%Y")
class(as.Date("20-09-1992", format = "%d-%m-%Y"))
We now assign this value to a matrix, imaginatively called Matrix:
Matrix <- matrix(NA,1,1)
Matrix[1,1] <- as.Date("20-09-1992", format = "%d-%m-%Y")
Matrix[1,1]
class(Matrix[1,1])
Suddenly the previously date formatted "20-09-1992" has become a numeric with the value 8298. I don't want a numeric with the value 8298, I want a date that looks like "20-09-1992" in date format.
So I was wondering whether this is simply how R works, and we are not allowed to assign dates to matrices and data frames (somehow I have managed to have dates in other matrices/data frames, but it beats me why those other times were different)? Is there a special method to assigning dates to data frames and matrices that I have missed and have failed to deduce from previous (somehow successful) attempts at assigning dates to data frames/matrices?
I don't think you can store dates in a matrix. Use a data frame or data table. If you must store dates in a matrix, you can use a matrix of lists.
Matrix <- matrix(NA,1,1)
Matrix[1,1] <- as.list(as.Date("20-09-1992", format = "%d-%m-%Y"),1)
Matrix
[[1]]
[1] "1992-09-20"
Edited: I also just re-read you had this issue with data frame. I'm not sure why.
mydate<-as.Date("20-09-1992", format = "%d-%m-%Y")
mydf<-data.frame(mydate)
mydf
mydate
1 1992-09-20
Edited: This has been a learning experience for me with R and dates. Apparently the date you supplied was converted to number of days since origin. Origin is defined as Jan 1st,1970. To convert this back to a date format at some point
Matrix
[,1]
[1,] 8298
as.Date(Matrix, origin ="1970-01-01")
[1] "1992-09-20"
try the following: First specify your date vector & then use
rownames(mat) <- as.character(date_vector)
the dates will appear as a text.
This happens mostly when we are loading Excel Workbook
You need to add detectDates = TRUE in the function
DataFrame <- read.xlsx("File_Nmae", sheet = 3, detectDates = TRUE)