Hi,
It's not as easy as I originally thought. Here is a revision with the
function beginEnd to get it done.
> date
key_column begin_date end_date
1 123456 2013-01-01 2014-01-01
2 123456 2013-07-01 2014-07-01
3 789102 2012-03-01 2014-03-01
4 789102 2015-02-01 2016-02-01
5 789102 2015-02-06 2016-02-06
> beginEnd
function()
{
date[order(date$key_column,date$begin_date),]
key <- numeric(0)
begin <- character(0)
end <- character(0)
currentKey <- as.numeric(date$key_column[1])
key <- c(key, currentKey)
currentBegin <- as.character(date$begin_date[1])
begin <- c(begin, currentBegin)
currentEnd <- as.character(date$end_date[1])
for (i in 2:length(date$key_column))
{
if (currentKey == as.numeric(date$key_column[i]))
{
if (currentEnd >= as.character(date$begin_date[i]))
{
currentEnd <- max(currentEnd, as.character(date$end_date[i]))
}
else
{
end <- c(end, currentEnd)
currentKey <- as.numeric(date$key_column[i])
key <- c(key, currentKey)
currentBegin <- as.character(date$begin_date[i])
begin <- c(begin, currentBegin)
currentEnd <- as.character(date$end_date[i])
}
if (i == length(date$key_column))
{
end <- c(end, currentEnd)
}
}
else
{
end <- c(end, currentEnd)
currentKey <- as.numeric(date$key_column[i])
key <- c(key, currentKey)
currentBegin <- as.character(date$begin_date[i])
begin <- c(begin, currentBegin)
currentEnd <- as.character(date$end_date[i])
if (i == length(date$key_column))
{
end <- list(end, currentEnd)
}
}
}
result <- cbind(key, begin, end)
colnames(result) <- c("key.column","begin.date","end.date")
return(result)
}
> beginEnd()
key.column begin.date end.date
[1,] "123456" "2013-01-01" "2014-07-01 "
[2,] "789102" "2012-03-01" "2014-03-01 "
[3,] "789102" "2015-02-01" "2016-02-06"
--
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