I am reading in an excel file in R and calculating the date 6 months prior to the date. If the date is falls on Weekend, need to change the date to the following weekday.
for example: if date is 2020-2-7, the six months prior is 2019-08-11. Which is Sunday.
How do I change the date to 2019-08-12?
I tried the following code:
date <- as.date.character("2020-2-7")
nxtd <- date-180
if(weekdays(nxtd)=="Saturday"){nxtd <- date-182} else if(weekdays(nxtd)=="Sunday"){nxtd <- date-181}
else{nxtd <- date-180}
this code gives an error/warning " the condition has length > 1 and only the first element will be used"
How do I resolve it?
library(lubridate)
d1 = as.Date("2020-2-9")
d2 = d1 - 180
if(weekdays(d2) %in% c("Saturday", "Sunday")){
floor_date(d2 - 3, "week") + 8
} else {
d2
}
Related
I am having trouble in using the date variable in my dataset to create categories of 6 months time period. I want to create these time period categories for years between 2017-1-1 and 2020-6-30. The time period categories for each year would be from 2017-1-1 to 2017-6-30, and 2017-7-1 to 2017-12-31 until 2020-6-30.
I have used the following two types of codes to create date categories but I am getting a similar error:
#CODE1
#checking for date class
myData <- str(myData)
myData #date in factor class
#convert to date class
date_class <- as.Date(myData$date, format = "%m/%d/%Y")
myData$date_class <- as.Date(myData$date, format = "%m/%d/%Y")
myData
#creating timeperiod category 1
date_cat <- NA
myData$date_cat[which(myData$date_class >= "2017-1-1" & myData$date_class < "2017-7-1")] <- 1
#CODE2
#converting to date format
myData$date <- strptime(myData$date,format="%m/%d/%Y")
myData$date <- as.POSIXct(myData$date)
myData
#creating timeperiod category 1
date_cat <- NA
myData$date_cat[which(myData$date >= "2017-1-1" & myData$date < "2017-7-1")] <- 1
For both the codes I am getting a similar error
Error in $<-.data.frame(*tmp*, date_cat, value = numeric(0)) :
replacement has 0 rows, data has 1123
Please help me with understanding where I am going wrong.
Thanks,
Priya
Here's a function (to.interval) that returns a time interval {0, 1, 2, 3, ...}, given parameters of the event date, index date, and interval width. Probably a good idea to include error checking in the function, so if for example the event date is prior to the anchor date, it returns NA.
df <- data.frame(event.date=as.Date(c("2017-01-01", "2017-08-01", "2018-04-30")))
to.interval <- function(anchor.date, future.date, interval.days){
round(as.integer(future.date - anchor.date) / interval.days, 0)}
df$interval <- to.interval(as.Date('2017-01-01'),
df$event.date, 180 )
df
Output
event.date interval
1 2017-01-01 0
2 2017-08-01 1
3 2018-04-30 3
Let's say we have this:
ex <- c('2012-41')
This represent the week 41 from the year 2012. How would I get the month from this?
Since a week can be between two months, I will be interested to get the month when that week started (here October).
Not duplicate to How to extract Month from date in R (do not have a standard date format like %Y-%m-%d).
you could try:
ex <- c('2019-10')
splitDate <- strsplit(ex, "-")
dateNew <- as.Date(paste(splitDate[[1]][1], splitDate[[1]][2], 1, sep="-"), "%Y-%U-%u")
monthSelected <- lubridate::month(dateNew)
3
I hope this helps!
This depends on the definition of week. See the discussion of %V and %W in ?strptime for two possible definitions of week. We use %V below but the function allows one to specify the other if desired. The function performs a sapply over the elements of x and for each such element it extracts the year into yr and forms a sequence of all dates for that year in sq. It then converts those dates to year-month and finds the first occurrence of the current component of x in that sequence, finally extracting the match's month.
yw2m <- function(x, fmt = "%Y-%V") {
sapply(x, function(x) {
yr <- as.numeric(substr(x, 1, 4))
sq <- seq(as.Date(paste0(yr, "-01-01")), as.Date(paste0(yr, "-12-31")), "day")
as.numeric(format(sq[which.max(format(sq, fmt) == x)], "%m"))
})
}
yw2m('2012-41')
## [1] 10
The following will add the week-of-year to an input of year-week formatted strings and return a vector of dates as character. The lubridate package weeks() function will add the dates corresponding to the end of the relevant week. Note for example I've added an additional case in your 'ex' variable to the 52nd week, and it returns Dec-31st
library(lubridate)
ex <- c('2012-41','2016-4','2018-52')
dates <- strsplit(ex,"-")
dates <- sapply(dates,function(x) {
year_week <- unlist(x)
year <- year_week[1]
week <- year_week[2]
start_date <- as.Date(paste0(year,'-01-01'))
date <- start_date+weeks(week)
#note here: OP asked for beginning of week.
#There's some ambiguity here, the above is end-of-week;
#uncommment here for beginning of week, just subtracted 6 days.
#I think this might yield inconsistent results, especially year-boundaries
#hence suggestion to use end of week. See below for possible solution
#date <- start_date+weeks(week)-days(6)
return (as.character(date))
})
Yields:
> dates
[1] "2012-10-14" "2016-01-29" "2018-12-31"
And to simply get the month from these full dates:
month(dates)
Yields:
> month(dates)
[1] 10 1 12
I have a column of strings in my data set formatted as year week (e.g. '201401' is equivalent to 7th April 2014, or the first fiscal week of the year)
I am trying to convert these to a proper date so I can manipulate them later, however I always receive the dame date for a given year, specifically the 14th of April.
e.g.
test_set <- c('201401', '201402', '201403')
as.Date(test_set, '%Y%U')
gives me:
[1] "2014-04-14" "2014-04-14" "2014-04-14"
Try something like this:
> test_set <- c('201401', '201402', '201403')
>
> extractDate <- function(dateString, fiscalStart = as.Date("2014-04-01")) {
+ week <- substr(dateString, 5, 6)
+ currentDate <- fiscalStart + 7 * as.numeric(week) - 1
+ currentDate
+ }
>
> extractDate(test_set)
[1] "2014-04-07" "2014-04-14" "2014-04-21"
Basically, I'm extracting the weeks from the start of the year, converting it to days and then adding that number of days to the start of the fiscal year (less 1 day to make things line up).
Not 100% sure what is your desired output but this may work
as.Date(paste0(substr(test_set, 1, 4), "-04-07")) +
(as.numeric(substr(test_set, 5, 6)) - 1) * 7
# [1] "2014-04-07" "2014-04-14" "2014-04-21"
I would like a function that counts the number of specific days per month..
i.e.. Nov '13 -> 5 fridays.. while Dec'13 would return 4 Fridays..
Is there an elegant function that would return this?
library(lubridate)
num_days <- function(date){
x <- as.Date(date)
start = floor_date(x, "month")
count = days_in_month(x)
d = wday(start)
sol = ifelse(d > 4, 5, 4) #estimate that is the first day of the month is after Thu or Fri then the week will have 5 Fridays
sol
}
num_days("2013-08-01")
num_days(today())
What would be a better way to do this?
1) Here d is the input, a Date class object, e.g. d <- Sys.Date(). The result gives the number of Fridays in the year/month that contains d. Replace 5 with 1 to get the number of Mondays:
first <- as.Date(cut(d, "month"))
last <- as.Date(cut(first + 31, "month")) - 1
sum(format(seq(first, last, "day"), "%w") == 5)
2) Alternately replace the last line with the following line. Here, the first term is the number of Fridays from the Epoch to the next Friday on or after the first of the next month and the second term is the number of Fridays from the Epoch to the next Friday on or after the first of d's month. Again, we replace all 5's with 1's to get the count of Mondays.
ceiling(as.numeric(last + 1 - 5 + 4) / 7) - ceiling(as.numeric(first - 5 + 4) / 7)
The second solution is slightly longer (although it has the same number of lines) but it has the advantage of being vectorized, i.e. d could be a vector of dates.
UPDATE: Added second solution.
There are a number of ways to do it. Here is one:
countFridays <- function(y, m) {
fr <- as.Date(paste(y, m, "01", sep="-"))
to <- fr + 31
dt <- seq(fr, to, by="1 day")
df <- data.frame(date=dt, mon=as.POSIXlt(dt)$mon, wday=as.POSIXlt(dt)$wday)
df <- subset(df, df$wday==5 & df$mon==df[1,"mon"])
return(nrow(df))
}
It creates the first of the months, and a day in the next months.
It then creates a data frame of month index (on a 0 to 11 range, but we only use this for comparison) and weekday.
We then subset to a) be in the same month and b) on a Friday. That is your result set, and
we return the number of rows as your anwser.
Note that this only uses base R code.
Without using lubridate -
#arguments to pass to function:
whichweekday <- 5
whichmonth <- 11
whichyear <- 2013
#function code:
firstday <- as.Date(paste('01',whichmonth,whichyear,sep="-"),'%d-%m-%Y')
lastday <- if(whichmonth == 12) { '31-12-2013' } else {seq(as.Date(firstday,'%d-%m-%Y'), length=2, by="1 month")[2]-1}
sum(
strftime(
seq.Date(
from = firstday,
to = lastday,
by = "day"),
'%w'
) == whichweekday)
This works for me in R:
# Setting up the first inner while-loop controller, the start of the next water year
NextH2OYear <- as.POSIXlt(firstDate)
NextH2OYear$year <- NextH2OYear$year + 1
NextH2OYear<-as.Date(NextH2OYear)
But this doesn't:
# Setting up the first inner while-loop controller, the start of the next water month
NextH2OMonth <- as.POSIXlt(firstDate)
NextH2OMonth$mon <- NextH2OMonth$mon + 1
NextH2OMonth <- as.Date(NextH2OMonth)
I get this error:
Error in as.Date.POSIXlt(NextH2OMonth) :
zero length component in non-empty POSIXlt structure
Any ideas why? I need to systematically add one year (for one loop) and one month (for another loop) and am comparing the resulting changed variables to values with a class of Date, which is why they are being converted back using as.Date().
Thanks,
Tom
Edit:
Below is the entire section of code. I am using RStudio (version 0.97.306). The code below represents a function that is passed an array of two columns (Date (CLass=Date) and Discharge Data (Class=Numeric) that are used to calculate the monthly averages. So, firstDate and lastDate are class Date and determined from the passed array. This code is adapted from successful code that calculates the yearly averages - there maybe one or two things I still need to change over, but I am prevented from error checking later parts due to the early errors I get in my use of POSIXlt. Here is the code:
MonthlyAvgDischarge<-function(values){
#determining the number of values - i.e. the number of rows
dataCount <- nrow(values)
# Determining first and last dates
firstDate <- (values[1,1])
lastDate <- (values[dataCount,1])
# Setting up vectors for results
WaterMonths <- numeric(0)
class(WaterMonths) <- "Date"
numDays <- numeric(0)
MonthlyAvg <- numeric(0)
# while loop variables
loopDate1 <- firstDate
loopDate2 <- firstDate
# Setting up the first inner while-loop controller, the start of the next water month
NextH2OMonth <- as.POSIXlt(firstDate)
NextH2OMonth$mon <- NextH2OMonth$mon + 1
NextH2OMonth <- as.Date(NextH2OMonth)
# Variables used in the loops
dayCounter <- 0
dischargeTotal <- 0
dischargeCounter <- 1
resultsCounter <- 1
loopCounter <- 0
skipcount <- 0
# Outer while-loop, controls the progression from one year to another
while(loopDate1 <= lastDate)
{
# Inner while-loop controls adding up the discharge for each water year
# and keeps track of day count
while(loopDate2 < NextH2OMonth)
{
if(is.na(values[resultsCounter,2]))
{
# Skip this date
loopDate2 <- loopDate2 + 1
# Skip this value
resultsCounter <- resultsCounter + 1
#Skipped counter
skipcount<-skipcount+1
} else{
# Adding up discharge
dischargeTotal <- dischargeTotal + values[resultsCounter,2]
}
# Adding a day
loopDate2 <- loopDate2 + 1
#Keeping track of days
dayCounter <- dayCounter + 1
# Keeping track of Dicharge position
resultsCounter <- resultsCounter + 1
}
# Adding the results/water years/number of days into the vectors
WaterMonths <- c(WaterMonths, as.Date(loopDate2, format="%mm/%Y"))
numDays <- c(numDays, dayCounter)
MonthlyAvg <- c(MonthlyAvg, round((dischargeTotal/dayCounter), digits=0))
# Resetting the left hand side variables of the while-loops
loopDate1 <- NextH2OMonth
loopDate2 <- NextH2OMonth
# Resetting the right hand side variable of the inner while-loop
# moving it one year forward in time to the next water year
NextH2OMonth <- as.POSIXlt(NextH2OMonth)
NextH2OMonth$year <- NextH2OMonth$Month + 1
NextH2OMonth<-as.Date(NextH2OMonth)
# Resettting vraiables that need to be reset
dayCounter <- 0
dischargeTotal <- 0
loopCounter <- loopCounter + 1
}
WaterMonths <- format(WaterMonthss, format="%mm/%Y")
# Uncomment the line below and return AvgAnnualDailyAvg if you want the water years also
# AvgAnnDailyAvg <- data.frame(WaterYears, numDays, YearlyDailyAvg)
return((MonthlyAvg))
}
Same error occurs in regular R. When doing it line by line, its not a problem, when running it as a script, it it.
Plain R
seq(Sys.Date(), length = 2, by = "month")[2]
seq(Sys.Date(), length = 2, by = "year")[2]
Note that this works with POSIXlt too, e.g.
seq(as.POSIXlt(Sys.Date()), length = 2, by = "month")[2]
mondate.
library(mondate)
now <- mondate(Sys.Date())
now + 1 # date in one month
now + 12 # date in 12 months
Mondate is bit smarter about things like mondate("2013-01-31")+ 1 which gives last day of February whereas seq(as.Date("2013-01-31"), length = 2, by = "month")[2] gives March 3rd.
yearmon If you don't really need the day part then yearmon may be preferable:
library(zoo)
now.ym <- yearmon(Sys.Date())
now.ym + 1/12 # add one month
now.ym + 1 # add one year
ADDED comment on POSIXlt and section on yearmon.
Here is you can add 1 month to a date in R, using package lubridate:
library(lubridate)
x <- as.POSIXlt("2010-01-31 01:00:00")
month(x) <- month(x) + 1
>x
[1] "2010-03-03 01:00:00 PST"
(note that it processed the addition correctly, as 31st of Feb doesn't exist).
Can you perhaps provide a reproducible example? What's in firstDate, and what version of R are you using? I do this kind of manipulation of POSIXlt dates quite often and it seems to work:
Sys.Date()
# [1] "2013-02-13"
date = as.POSIXlt(Sys.Date())
date$mon = date$mon + 1
as.Date(date)
# [1] "2013-03-13"