[R] Loop With Dates

[Richard O'Keefe]

Is this what you're after?

> df <- data.frame(
+         Date = as.Date(c("2018-03-29", "2018-03-29", "2018-03-29",
+                          "2018-03-30", "2018-03-30", "2018- ..." ...
[TRUNCATED]

> df$count <- cumsum(c(TRUE, diff(df$Date) > 0))
> df
        Date count
1 2018-03-29     1
2 2018-03-29     1
3 2018-03-29     1
4 2018-03-30     2
5 2018-03-30     2
6 2018-03-30     2
7 2018-03-31     3
8 2018-03-31     3
9 2018-03-31     3

No extra libraries needed.  Whenever you want a vector that counts something,
cumsum of a logical vector is a good thing to try.

On Sat, 21 Sep 2019 at 05:47, Phillip Heinrich <herd_dog using cox.net> wrote:
>
> With the data snippet below I’m trying to increment the “count” vector by one each time the date changes.
>
>          Date count
> 1   2018-03-29     1
> 2   2018-03-29     1
> 3   2018-03-29     1
> 81  2018-03-30     1
> 82  2018-03-30     1
> 83  2018-03-30     1
> 165 2018-03-31     1
> 166 2018-03-31     1
> 167 2018-03-31     1
>
>
>             >
>
>
>
> I can get count to change when the date changes with the following code:
>
> test2 <- transform(test2,
> +                   count = ifelse(Date == lag(Date,1),count,count+1))
> > test2
>           Date count
> 1   2018-03-29    NA
> 2   2018-03-29     1
> 3   2018-03-29     1
> 81  2018-03-30     2
> 82  2018-03-30     1
> 83  2018-03-30     1
> 165 2018-03-31     2
> 166 2018-03-31     1
> 167 2018-03-31     1
>
>
>
>
>
>
>
> ...but I want all three March 30 rows to have a count of 2 and the March 31 rows to be equal to 3.  Any suggestions?
>
> Thanks.
>         [[alternative HTML version deleted]]
>
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