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Clash Royale CLAN TAG

Manipulating dates alongside consecutive results

I need some help working with consecutive results.

Here is my sample data:

df <- structure(list(idno = c(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2,
2, 2, 2), result = structure(c(1L, 2L, 2L, 1L, 1L, 1L, 1L, 1L,
1L, 1L, 2L, 1L, 1L, 2L, 2L, 2L), .Label = c("Negative", "Positive"
), class = c("ordered", "factor")), samp_date = structure(c(15909,
15938, 15979, 16007, 16041, 16080, 16182, 16504, 16576, 16645,
16721, 16745, 17105, 17281, 17416, 17429), class = "Date")), class = "data.frame", row.names = c(NA,
-16L))


The 'idno' represents individual people who had a test with 'result' on a given date ('samp_date').

From each individual person, I need to find the earliest consecutive 'Negatives' and return the date of the first 'negative' result. To return this date, the consecutive negatives must span >30 days with no 'positive' results.

The example answer for idno == 1 would be 2013-10-29, and 2015-11-06 for idno == 2.

I have tried using rle(as.character(df$result)) but have struggled to understand how to apply this to grouped data.

rle(as.character(df$result))

I would prefer an approach that uses dplyr or data.table.

Thanks for any help.

3 Answers
3

A dplyr based solution can be achieved by creating a group of consecutive occurrence of result column and then finally taking 1st occurrence that meets criteria:

dplyr

result

library(dplyr)
df %>% mutate(samp_date = as.Date(samp_date)) %>%
group_by(idno) %>%
arrange(samp_date) %>%
mutate(result_grp = cumsum(as.character(result)!=lag(as.character(result),default=""))) %>%
group_by(idno, result_grp) %>%
filter( result == "Negative" & (max(samp_date) - min(samp_date) )>=30) %>%
slice(1) %>%
ungroup() %>%
select(-result_grp)

# # A tibble: 2 x 3
# idno result samp_date
# <dbl> <ord> <date>
# 1 1.00 Negative 2013-10-29
# 2 2.00 Negative 2015-11-06


Similar to @MKR's answer, you can make a grouping variable and summarize in data.table:

library(data.table)
setDT(df)[, samp_date := as.IDate(samp_date)]

# summarize by grouping var g = rleid(idno, result)
runDT = df[, .(
start = first(samp_date),
end = last(samp_date),
dur = difftime(last(samp_date), first(samp_date), units="days")
), by=.(idno, result, g = rleid(idno, result))]

# idno result g start end dur
# 1: 1 Negative 1 2013-07-23 2013-07-23 0 days
# 2: 1 Positive 2 2013-08-21 2013-10-01 41 days
# 3: 1 Negative 3 2013-10-29 2015-07-29 638 days
# 4: 2 Positive 4 2015-10-13 2015-10-13 0 days
# 5: 2 Negative 5 2015-11-06 2016-10-31 360 days
# 6: 2 Positive 6 2017-04-25 2017-09-20 148 days

# find rows meeting the criterion
w = runDT[.(idno = unique(idno), result = "Negative", min_dur = 30),
on=.(idno, result, dur >= min_dur), mult="first", which=TRUE]

# filter
runDT[w]

# idno result g start end dur
# 1: 1 Negative 3 2013-10-29 2015-07-29 638 days
# 2: 2 Negative 5 2015-11-06 2016-10-31 360 days


w

dur

min_dur

library(dplyr)
df %>% group_by(idno) %>%
mutate(time_diff = ifelse(result=="Negative" & lead(result)=='Negative', samp_date - lead(samp_date),0),
ConsNegDate = min(samp_date[which(abs(time_diff)>30)]))


# A tibble: 16 x 5
# Groups: idno [2]
idno result samp_date time_diff ConsNegDate
<dbl> <ord> <date> <dbl> <date>
1 1 Negative 2013-07-23 0 2013-10-29
2 1 Positive 2013-08-21 0 2013-10-29
3 1 Positive 2013-10-01 0 2013-10-29
4 1 Negative 2013-10-29 -34 2013-10-29
5 1 Negative 2013-12-02 -39 2013-10-29
6 1 Negative 2014-01-10 -102 2013-10-29
7 1 Negative 2014-04-22 -322 2013-10-29
8 1 Negative 2015-03-10 -72 2013-10-29
9 1 Negative 2015-05-21 -69 2013-10-29
10 1 Negative 2015-07-29 NA 2013-10-29
11 2 Positive 2015-10-13 0 2015-11-06
12 2 Negative 2015-11-06 -360 2015-11-06
13 2 Negative 2016-10-31 0 2015-11-06
14 2 Positive 2017-04-25 0 2015-11-06
15 2 Positive 2017-09-07 0 2015-11-06
16 2 Positive 2017-09-20 0 2015-11-06


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