The challenge is a data.frame with with one group variable (id) and two date variables (start and stop). The date intervals are irregular and I'm trying to calculate the uninterrupted interval in days starting from the first startdate per group.
Example data:
data <- data.frame(
id = c(1, 2, 2, 3, 3, 3, 3, 3, 4, 5),
start = as.Date(c("2016-02-18", "2016-12-07", "2016-12-12", "2015-04-10",
"2015-04-12", "2015-04-14", "2015-05-15", "2015-07-14",
"2010-12-08", "2011-03-09")),
stop = as.Date(c("2016-02-19", "2016-12-12", "2016-12-13", "2015-04-13",
"2015-04-22", "2015-05-13", "2015-07-13", "2015-07-15",
"2010-12-10", "2011-03-11"))
)
> data
id start stop
1 1 2016-02-18 2016-02-19
2 2 2016-12-07 2016-12-12
3 2 2016-12-12 2016-12-13
4 3 2015-04-10 2015-04-13
5 3 2015-04-12 2015-04-22
6 3 2015-04-14 2015-05-13
7 3 2015-05-15 2015-07-13
8 3 2015-07-14 2015-07-15
9 4 2010-12-08 2010-12-10
10 5 2011-03-09 2011-03-11
The aim would a data.frame like this:
id start stop duration_from_start
1 1 2016-02-18 2016-02-19 2
2 2 2016-12-07 2016-12-12 7
3 2 2016-12-12 2016-12-13 7
4 3 2015-04-10 2015-04-13 34
5 3 2015-04-12 2015-04-22 34
6 3 2015-04-14 2015-05-13 34
7 3 2015-05-15 2015-07-13 34
8 3 2015-07-14 2015-07-15 34
9 4 2010-12-08 2010-12-10 3
10 5 2011-03-09 2011-03-11 3
Or this:
id start stop duration_from_start
1 1 2016-02-18 2016-02-19 2
2 2 2016-12-07 2016-12-13 7
3 3 2015-04-10 2015-05-13 34
4 4 2010-12-08 2010-12-10 3
5 5 2011-03-09 2011-03-11 3
It's important to identify the gap from row 6 to 7 and to take this point as the maximum interval (34 days). The interval 2018-10-01to 2018-10-01 would be counted as 1.
My usual lubridate approaches don't work with this example (interval %within lag(interval)).
Any idea?
library(magrittr)
library(data.table)
setDT(data)
first_int <- function(start, stop){
ind <- rleid((start - shift(stop, fill = Inf)) > 0) == 1
list(start = min(start[ind]),
stop = max(stop[ind]))
}
newdata <-
data[, first_int(start, stop), by = id] %>%
.[, duration := stop - start + 1]
# id start stop duration
# 1: 1 2016-02-18 2016-02-19 2 days
# 2: 2 2016-12-07 2016-12-13 7 days
# 3: 3 2015-04-10 2015-05-13 34 days
# 4: 4 2010-12-08 2010-12-10 3 days
# 5: 5 2011-03-09 2011-03-11 3 days
Related
I have a dataset containing time periods during which an intervention is happening. We have two types of interventions. I have the start and end date of each intervention. I would now like to extract the time (in days) when there is no overlap between the two types and how much overlap there is.
Here's an example dataset:
data <- data.table( id = seq(1,21),
type = as.character(c(1,2,2,2,2,2,2,2,1,1,1,1,1,2,1,2,1,1,1,1,1)),
start_dt = as.Date(c("2015-01-09", "2015-04-14", "2015-06-19", "2015-10-30", "2016-03-01", "2016-05-24",
"2016-08-03", "2017-08-18", "2017-08-18", "2018-02-01", "2018-05-07", "2018-08-09",
"2019-01-31", "2019-03-22", "2019-05-16", "2019-11-04", "2019-11-04", "2020-02-06",
"2020-05-28", "2020-08-25", "2020-12-14")),
end_dt = as.Date(c("2017-07-24", "2015-05-04", "2015-08-27", "2015-11-19", "2016-03-21", "2016-06-09",
"2017-07-18", "2019-02-21", "2018-01-23", "2018-04-25", "2018-07-29", "2019-01-15",
"2019-04-24", "2019-09-13", "2019-10-13", "2020-12-23", "2020-01-26", "2020-04-29",
"2020-08-19", "2020-11-16", "2021-03-07")))
> data
id type start_dt end_dt
1: 1 1 2015-01-09 2017-07-24
2: 2 2 2015-04-14 2015-05-04
3: 3 2 2015-06-19 2015-08-27
4: 4 2 2015-10-30 2015-11-19
5: 5 2 2016-03-01 2016-03-21
6: 6 2 2016-05-24 2016-06-09
7: 7 2 2016-08-03 2017-07-18
8: 8 2 2017-08-18 2019-02-21
9: 9 1 2017-08-18 2018-01-23
10: 10 1 2018-02-01 2018-04-25
11: 11 1 2018-05-07 2018-07-29
12: 12 1 2018-08-09 2019-01-15
13: 13 1 2019-01-31 2019-04-24
14: 14 2 2019-03-22 2019-09-13
15: 15 1 2019-05-16 2019-10-13
16: 16 2 2019-11-04 2020-12-23
17: 17 1 2019-11-04 2020-01-26
18: 18 1 2020-02-06 2020-04-29
19: 19 1 2020-05-28 2020-08-19
20: 20 1 2020-08-25 2020-11-16
21: 21 1 2020-12-14 2021-03-07
Here's a plot of the data for a better view of what I want to know:
library(ggplot2)
ggplot(data = data,
aes(x = start_dt, xend = end_dt, y = id, yend = id, color = type)) +
geom_segment(size = 2) +
xlab("") +
ylab("") +
theme_bw()
I'll describe the first part of the example: we have an intervention of type 1 from 2015-01-09 until 2017-07-24. From 2015-04-14 however, also intervention type 2 is happening. This means that we only have "pure" type 1 from 2015-01-09 to 2015-04-13, which is 95 days.
Then we have an overlapping period from 2015-04-14 to 2015-05-04, which is 21 days. Then we again have a period with only type 1 from 2015-05-05 to 2015-06-18, which is 45 days. In total, we now have had (95 + 45 =) 140 days of "pure" type 1 and 21 days of overlap. Then we continue like this for the entire time period.
I would like to know the total time (in days) of "pure" type 1, "pure" type 2 and overlap.
Alternatively, if also possible, I would like to organise the data such, that I get all the seperate time periods extracted, meaning that the data would look something like this (type 3 = overlap):
> data_adjusted
id type start_dt end_dt
1: 1 1 2015-01-09 2015-04-14
2: 2 3 2015-04-15 2015-05-04
3: 3 1 2015-05-05 2015-06-18
4: 4 3 2015-06-19 2015-08-27
........
The time in days spent in each intervention type can then easily be calculated from data_adjuted.
I have similar answers using dplyr or just marking overlapping time periods, but I have not found an answer to my specific case.
Is there an efficient way to calculate this using data.table?
This method does a small explosion of looking at all dates in the range, so it may not scale very well if your data gets large.
library(data.table)
alldates <- data.table(date = seq(min(data$start_dt), max(data$end_dt), by = "day"))
data[alldates, on = .(start_dt <= date, end_dt >= date)] %>%
.[, .N, by = .(start_dt, type) ] %>%
.[ !is.na(type), ] %>%
dcast(start_dt ~ type, value.var = "N") %>%
.[, r := do.call(rleid, .SD), .SDcols = setdiff(colnames(.), "start_dt") ] %>%
.[, .(type = fcase(is.na(`1`[1]), "2", is.na(`2`[1]), "1", TRUE, "3"),
start_dt = min(start_dt), end_dt = max(start_dt)), by = r ]
# r type start_dt end_dt
# <int> <char> <Date> <Date>
# 1: 1 1 2015-01-09 2015-04-13
# 2: 2 3 2015-04-14 2015-05-04
# 3: 3 1 2015-05-05 2015-06-18
# 4: 4 3 2015-06-19 2015-08-27
# 5: 5 1 2015-08-28 2015-10-29
# 6: 6 3 2015-10-30 2015-11-19
# 7: 7 1 2015-11-20 2016-02-29
# 8: 8 3 2016-03-01 2016-03-21
# 9: 9 1 2016-03-22 2016-05-23
# 10: 10 3 2016-05-24 2016-06-09
# 11: 11 1 2016-06-10 2016-08-02
# 12: 12 3 2016-08-03 2017-07-18
# 13: 13 1 2017-07-19 2017-07-24
# 14: 14 3 2017-08-18 2018-01-23
# 15: 15 2 2018-01-24 2018-01-31
# 16: 16 3 2018-02-01 2018-04-25
# 17: 17 2 2018-04-26 2018-05-06
# 18: 18 3 2018-05-07 2018-07-29
# 19: 19 2 2018-07-30 2018-08-08
# 20: 20 3 2018-08-09 2019-01-15
# 21: 21 2 2019-01-16 2019-01-30
# 22: 22 3 2019-01-31 2019-02-21
# 23: 23 1 2019-02-22 2019-03-21
# 24: 24 3 2019-03-22 2019-04-24
# 25: 25 2 2019-04-25 2019-05-15
# 26: 26 3 2019-05-16 2019-09-13
# 27: 27 1 2019-09-14 2019-10-13
# 28: 28 3 2019-11-04 2020-01-26
# 29: 29 2 2020-01-27 2020-02-05
# 30: 30 3 2020-02-06 2020-04-29
# 31: 31 2 2020-04-30 2020-05-27
# 32: 32 3 2020-05-28 2020-08-19
# 33: 33 2 2020-08-20 2020-08-24
# 34: 34 3 2020-08-25 2020-11-16
# 35: 35 2 2020-11-17 2020-12-13
# 36: 36 3 2020-12-14 2020-12-23
# 37: 37 1 2020-12-24 2021-03-07
# r type start_dt end_dt
It drops the id field, I don't know how to map it well back to your original data.
#r2evans solution is more complete, but if you want to explore the use offoverlaps you can start with something like this:
#split into two frames
data = split(data,by="type")
# key the second frame
setkey(data[[2]], start_dt, end_dt)
# create the rows that have overlaps
overlap = foverlaps(data[[1]],data[[2]], type="any", nomatch=0)
# get the overlapping time periods
overlap[, .(start_dt = max(start_dt,i.start_dt), end_dt=min(end_dt,i.end_dt)), by=1:nrow(overlap)][,type:=3]
Output:
nrow start_dt end_dt type
1: 1 2015-04-14 2015-05-04 3
2: 2 2015-06-19 2015-08-27 3
3: 3 2015-10-30 2015-11-19 3
4: 4 2016-03-01 2016-03-21 3
5: 5 2016-05-24 2016-06-09 3
6: 6 2016-08-03 2017-07-18 3
7: 7 2017-08-18 2018-01-23 3
8: 8 2018-02-01 2018-04-25 3
9: 9 2018-05-07 2018-07-29 3
10: 10 2018-08-09 2019-01-15 3
11: 11 2019-01-31 2019-02-21 3
12: 12 2019-03-22 2019-04-24 3
13: 13 2019-05-16 2019-09-13 3
14: 14 2019-11-04 2020-01-26 3
15: 15 2020-02-06 2020-04-29 3
16: 16 2020-05-28 2020-08-19 3
17: 17 2020-08-25 2020-11-16 3
18: 18 2020-12-14 2020-12-23 3
The sum of those overlap days is 1492.
These are subsets of two dataframes.
df1:
plot
mean_first_flower_date
gdd
1
2019-07-15
60
1
2019-07-21
50
1
2019-07-23
78
2
2019-05-13
100
2
2019-05-22
173
2
2019-05-25
245
(cont.)
df2:
plot
date
flowers
1
2019-07-12
2
1
2019-07-13
9
1
2019-07-14
3
1
2019-07-15
3
2
2019-05-12
10
2
2019-05-13
10
2
2019-05-14
14
2
2019-05-15
17
(cont.)
df2 has some matching dates with df1 but sometimes the dates are off for one or a couple days (highlighted in bold).
I would like to group both dfs based on both 'date' and 'plot', keeping df2, without losing 'gdd' data from df1.
This will happen if, for example, I inner_join both dfs because the dates will not match.
So if a date in df1 is one to three days earlier or later than what it's possible to match in df2, it's fine because the dates are relatively close. This is tricky because I want this data replacement only if there is not data available in df1 for that data range.
My goal is to have something like this:
plot
date
flowers
gdd
1
2019-07-12
2
60
1
2019-07-13
9
60
1
2019-07-14
3
60
1
2019-07-15
3
60
2
2019-05-12
10
100
2
2019-05-13
10
100
2
2019-05-14
14
100
2
2019-05-15
17
100
Is it possible to do?
I greatly appreciate any help!
Thanks!
I think a 'rolling join' from the data.table package can handle this:
library(data.table)
setDT(df1)
setDT(df2)
df1[, mean_first_flower_date := as.Date(mean_first_flower_date)]
df2[, date := as.Date(date)]
df1[df2, on=c("plot","mean_first_flower_date==date"), roll=3, rollends=TRUE]
# plot mean_first_flower_date gdd flowers
#1: 1 2019-07-12 60 2
#2: 1 2019-07-13 60 9
#3: 1 2019-07-14 60 3
#4: 1 2019-07-15 60 3
#5: 2 2019-05-12 100 10
#6: 2 2019-05-13 100 10
#7: 2 2019-05-14 100 14
#8: 2 2019-05-15 100 17
Using this data:
df1 <- read.table(text="plot mean_first_flower_date gdd
1 2019-07-15 60
1 2019-07-21 50
1 2019-07-23 78
2 2019-05-13 100
2 2019-05-22 173
2 2019-05-25 245", header=TRUE)
df2 <- read.table(text="plot date flowers
1 2019-07-12 2
1 2019-07-13 9
1 2019-07-14 3
1 2019-07-15 3
2 2019-05-12 10
2 2019-05-13 10
2 2019-05-14 14
2 2019-05-15 17", header=TRUE)
Try fill from dplyr. use this syntax
df2 %>% left_join(df1, by = c("plot" = "plot", "date" = "mean_first_flower_date")) %>%
fill(gdd, .direction = "up")
plot date flowers gdd
1 1 2019-07-12 2 60
2 1 2019-07-13 9 60
3 1 2019-07-14 3 60
4 1 2019-07-15 3 60
5 2 2019-05-12 10 100
6 2 2019-05-13 10 100
7 2 2019-05-14 14 NA
8 2 2019-05-15 17 NA
As you can notice there are two NAs in the last two rows which shouldn't be there if you'll join your actual df2 where these rows will be filled by 173 as there will be a match for 2019-05-22. Still if you want to fill the last NA rows, if any, you can use fill again with .direction = "down"
df2 %>% left_join(df1, by = c("plot" = "plot", "date" = "mean_first_flower_date")) %>%
fill(gdd, .direction = "up") %>% fill(gdd, .direction = "down")
plot date flowers gdd
1 1 2019-07-12 2 60
2 1 2019-07-13 9 60
3 1 2019-07-14 3 60
4 1 2019-07-15 3 60
5 2 2019-05-12 10 100
6 2 2019-05-13 10 100
7 2 2019-05-14 14 100
8 2 2019-05-15 17 100
I received a set of dates, but it turns out that time is reported in days since 01-01-1960 in this specific data set.
D_INDDTO
1 20758
2 20856
3 21062
4 19740
5 21222
6 21203
The specific date of interest for Patient 1 is 20758 days since 01-01-60
I want to create a new covariate u$date containing the specific date of interest i d%m%y%. I tried
library(tidyverse)
u %>% mutate(date=as.date(D_INDDTO,origin="1960-01-01")
But that did not solve it.
u <- structure(list(D_INDDTO = c(20758, 20856, 21062, 19740, 21222,
21203, 20976, 20895, 18656, 18746)), row.names = c(NA, 10L), class = "data.frame")
Try this:
#Code 1
u %>% mutate(date=as.Date("1960-01-01")+D_INDDTO)
Output:
D_INDDTO date
1 20758 2016-10-31
2 20856 2017-02-06
3 21062 2017-08-31
4 19740 2014-01-17
5 21222 2018-02-07
6 21203 2018-01-19
7 20976 2017-06-06
8 20895 2017-03-17
9 18656 2011-01-29
10 18746 2011-04-29
Or this:
#Code 2
u %>% mutate(date=as.Date(D_INDDTO,origin="1960-01-01"))
Output:
D_INDDTO date
1 20758 2016-10-31
2 20856 2017-02-06
3 21062 2017-08-31
4 19740 2014-01-17
5 21222 2018-02-07
6 21203 2018-01-19
7 20976 2017-06-06
8 20895 2017-03-17
9 18656 2011-01-29
10 18746 2011-04-29
Or this:
#Code 3
u %>% mutate(date=format(as.Date(D_INDDTO,origin="1960-01-01"),'%d%m%y'))
Output:
D_INDDTO date
1 20758 311016
2 20856 060217
3 21062 310817
4 19740 170114
5 21222 070218
6 21203 190118
7 20976 060617
8 20895 170317
9 18656 290111
10 18746 290411
If more customization is required:
#Code 4
u %>% mutate(date=format(as.Date(D_INDDTO,origin="1960-01-01"),'%d-%m-%Y'))
Output:
D_INDDTO date
1 20758 31-10-2016
2 20856 06-02-2017
3 21062 31-08-2017
4 19740 17-01-2014
5 21222 07-02-2018
6 21203 19-01-2018
7 20976 06-06-2017
8 20895 17-03-2017
9 18656 29-01-2011
10 18746 29-04-2011
I have a dataset that contains the residence period (start.date to end.date) of marked individuals (ID) at different sites. My goal is to generate a column that tells me the average number of other individuals per day that were also present at the same site (across the total residence period of each individual).
To do this, I need to determine the total number of individuals that were present per site on each date, summed across the total residence period of each individual. Ultimately, I will divide this sum by the total residence days of each individual to calculate the average. Can anyone help me accomplish this?
I calculated the total number of residence days (total.days) using lubridate and dplyr
mutate(total.days = end.date - start.date + 1)
site ID start.date end.date total.days
1 1 16 5/24/17 6/5/17 13
2 1 46 4/30/17 5/20/17 21
3 1 26 4/30/17 5/23/17 24
4 1 89 5/5/17 5/13/17 9
5 1 12 5/11/17 5/14/17 4
6 2 14 5/4/17 5/10/17 7
7 2 18 5/9/17 5/29/17 21
8 2 19 5/24/17 6/10/17 18
9 2 39 5/5/17 5/18/17 14
First of all, it is always advisable to give a sample of the data in a more friendly format using dput(yourData) so that other can easily regenerate your data. Here is the output of dput() you could better be sharing:
> dput(dat)
structure(list(site = c(1, 1, 1, 1, 1, 2, 2, 2, 2), ID = c(16,
46, 26, 89, 12, 14, 18, 19, 39), start.date = structure(c(17310,
17286, 17286, 17291, 17297, 17290, 17295, 17310, 17291), class = "Date"),
end.date = structure(c(17322, 17306, 17309, 17299, 17300,
17296, 17315, 17327, 17304), class = "Date")), class = "data.frame", row.names =
c(NA,
-9L))
To do this easily we first need to unpack the start.date and end.date to individual dates:
newDat <- data.frame()
for (i in 1:nrow(dat)){
expand <- data.frame(site = dat$site[i],
ID = dat$ID[i],
Dates = seq.Date(dat$start.date[i], dat$end.date[i], 1))
newDat <- rbind(newDat, expand)
}
newDat
site ID Dates
1 1 16 2017-05-24
2 1 16 2017-05-25
3 1 16 2017-05-26
4 1 16 2017-05-27
5 1 16 2017-05-28
6 1 16 2017-05-29
7 1 16 2017-05-30
. . .
. . .
Then we calculate the number of other individuals present in each site in each day:
individualCount = newDat %>%
group_by(site, Dates) %>%
summarise(individuals = n_distinct(ID) - 1)
individualCount
# A tibble: 75 x 3
# Groups: site [?]
site Dates individuals
<dbl> <date> <int>
1 1 2017-04-30 1
2 1 2017-05-01 1
3 1 2017-05-02 1
4 1 2017-05-03 1
5 1 2017-05-04 1
6 1 2017-05-05 2
7 1 2017-05-06 2
8 1 2017-05-07 2
9 1 2017-05-08 2
10 1 2017-05-09 2
# ... with 65 more rows
Then, we augment our data with the new information using left_join() and calculate the required average:
newDat <- left_join(newDat, individualCount, by = c("site", "Dates")) %>%
group_by(site, ID) %>%
summarise(duration = max(Dates) - min(Dates)+1,
av.individuals = mean(individuals))
newDat
# A tibble: 9 x 4
# Groups: site [?]
site ID duration av.individuals
<dbl> <dbl> <time> <dbl>
1 1 12 4 0.75
2 1 16 13 0
3 1 26 24 1.42
4 1 46 21 1.62
5 1 89 9 1.33
6 2 14 7 1.14
7 2 18 21 0.875
8 2 19 18 0.333
9 2 39 14 1.14
The final step is to add the required column to the original dataset (dat) again with left_join():
dat %>% left_join(newDat, by = c("site", "ID"))
dat
site ID start.date end.date duration av.individuals
1 1 16 2017-05-24 2017-06-05 13 days 0.000000
2 1 46 2017-04-30 2017-05-20 21 days 1.619048
3 1 26 2017-04-30 2017-05-23 24 days 1.416667
4 1 89 2017-05-05 2017-05-13 9 days 2.333333
5 1 12 2017-05-11 2017-05-14 4 days 2.750000
6 2 14 2017-05-04 2017-05-10 7 days 1.142857
7 2 18 2017-05-09 2017-05-29 21 days 0.857143
8 2 19 2017-05-24 2017-06-10 18 days 0.333333
9 2 39 2017-05-05 2017-05-18 14 days 1.142857
I have a dataframe that contains the dates of multiple types of events.
df <- data.frame(date=as.Date(c("06/07/2000","15/09/2000","15/10/2000"
,"03/01/2001","17/03/2001","23/04/2001",
"26/05/2001","01/06/2001",
"30/06/2001","02/07/2001","15/07/2001"
,"21/12/2001"), "%d/%m/%Y"),
event_type=c(0,4,1,2,4,1,0,2,3,3,4,3))
date event_type
---------------- ----------
1 2000-07-06 0
2 2000-09-15 4
3 2000-10-15 1
4 2001-01-03 2
5 2001-03-17 4
6 2001-04-23 1
7 2001-05-26 0
8 2001-06-01 2
9 2001-06-30 3
10 2001-07-02 3
11 2001-07-15 4
12 2001-12-21 3
I am trying to calculate the days between each event type so the output looks like the below:
date event_type days_since_last_event
---------------- ---------- ---------------------
1 2000-07-06 0 NA
2 2000-09-15 4 NA
3 2000-10-15 1 NA
4 2001-01-03 2 NA
5 2001-03-17 4 183
6 2001-04-23 1 190
7 2001-05-26 0 324
8 2001-06-01 2 149
9 2001-06-30 3 NA
10 2001-07-02 3 2
11 2001-07-15 4 120
12 2001-12-21 3 172
I have benefited from the answers from these two previous posts but have not been able to address my specific problem in R; multiple event types.
Calculate elapsed time since last event
Calculate days since last event in R
Below is as far as I have gotten. I have not been able to leverage the last event index to calculate the last event date.
df <- cbind(df, as.vector(data.frame(count=ave(df$event_type==df$event_type,
df$event_type, FUN=cumsum))))
df <- rename(df, c("count" = "last_event_index"))
date event_type last_event_index
--------------- ------------- ----------------
1 2000-07-06 0 1
2 2000-09-15 4 1
3 2000-10-15 1 1
4 2001-01-03 2 1
5 2001-03-17 4 2
6 2001-04-23 1 2
7 2001-05-26 0 2
8 2001-06-01 2 2
9 2001-06-30 3 1
10 2001-07-02 3 2
11 2001-07-15 4 3
12 2001-12-21 3 3
We can use diff to get the difference between adjacent 'date' after grouping by 'event_type'. Here, I am using data.table approach by converting the 'data.frame' to 'data.table' (setDT(df)), grouped by 'event_type', we get the diff of 'date'.
library(data.table)
setDT(df)[,days_since_last_event :=c(NA,diff(date)) , by = event_type]
df
# date event_type days_since_last_event
# 1: 2000-07-06 0 NA
# 2: 2000-09-15 4 NA
# 3: 2000-10-15 1 NA
# 4: 2001-01-03 2 NA
# 5: 2001-03-17 4 183
# 6: 2001-04-23 1 190
# 7: 2001-05-26 0 324
# 8: 2001-06-01 2 149
# 9: 2001-06-30 3 NA
#10: 2001-07-02 3 2
#11: 2001-07-15 4 120
#12: 2001-12-21 3 172
Or as #Frank mentioned in the comments, we can also use shift (from version v1.9.5+ onwards) to get the lag (by default, the type='lag') of 'date' and subtract from the 'date'.
setDT(df)[, days_since_last_event := as.numeric(date-shift(date,type="lag")),
by = event_type]
The base R version of this is to use split/lapply/rbind to generate the new column.
> do.call(rbind,
lapply(
split(df, df$event_type),
function(d) {
d$dsle <- c(NA, diff(d$date)); d
}
)
)
date event_type dsle
0.1 2000-07-06 0 NA
0.7 2001-05-26 0 324
1.3 2000-10-15 1 NA
1.6 2001-04-23 1 190
2.4 2001-01-03 2 NA
2.8 2001-06-01 2 149
3.9 2001-06-30 3 NA
3.10 2001-07-02 3 2
3.12 2001-12-21 3 172
4.2 2000-09-15 4 NA
4.5 2001-03-17 4 183
4.11 2001-07-15 4 120
Note that this returns the data in a different order than provided; you can re-sort by date or save the original indices if you want to preserve that order.
Above, #akrun has posted the data.tables approach, the parallel dplyr approach would be straightforward as well:
library(dplyr)
df %>% group_by(event_type) %>% mutate(days_since_last_event=date - lag(date, 1))
Source: local data frame [12 x 3]
Groups: event_type [5]
date event_type days_since_last_event
(date) (dbl) (dfft)
1 2000-07-06 0 NA days
2 2000-09-15 4 NA days
3 2000-10-15 1 NA days
4 2001-01-03 2 NA days
5 2001-03-17 4 183 days
6 2001-04-23 1 190 days
7 2001-05-26 0 324 days
8 2001-06-01 2 149 days
9 2001-06-30 3 NA days
10 2001-07-02 3 2 days
11 2001-07-15 4 120 days
12 2001-12-21 3 172 days