[R] flag records

[Avi Gross]

Lots of people here are touchy about homework and I can understand that.
But sharing code and saying where you are stuck is a plus for me as compared to asking someone to do it all.
So, without commenting on whether your shown code is right, assuming youhave a data.frame object sorted as described so that adjacent rows MIGHT be what you want, then look into a function called lag() which may be in the stats package or dplyr.
OR, consider what it means to loop though an index from 2 to the number of rows and how that lets you look at adjacent entries and even modify them.


-----Original Message-----
From: Val <valkremk using gmail.com>
To: r-help using R-project.org (r-help using r-project.org) <r-help using r-project.org>
Sent: Tue, Apr 26, 2022 6:17 pm
Subject: [R] flag records

Hi All,

I want to flag a record based on the following condition.
The variables  in the sample data are
State, name, day, text, ddate

Sort the data by State, name, day ddate,

Within  State, name, day
    assign consecutive number for each row
    find the date difference between consecutive rows,
    if the difference is less than 50 days and the text string in
previous and current rows  are the same then flag the record as X,
otherwise Y.

Here is  sample data and my attempt,

DF<-read.table(text="State name day text ddate
  CA A 1 xch 2014/09/16
  CA A 2 xck 2015/5/29
  CA A 2 xck 2015/6/18
  CA A 2 xcm 2015/8/3
  CA A 2 xcj 2015/8/26
  FL B 3 xcu  2017/7/23
  FL B 3 xcl  2017/7/03
  FL B 3 xmc  2017/7/26
  FL B 3 xca  2017/3/17
  FL B 3 xcb  2017/4/8
  FL B 4 xhh  2017/3/17
  FL B 4 xhh  2017/1/29",header=TRUE)

  DF$ddate  <- as.Date (as.Date(DF$ddate),  format="%Y/%m/%d" )
  DF3        <- DF[order(DF$State,DF$name,DF$day,xtfrm(DF$ddate)), ]
  DF3$C      <- with(DF3, ave(State, name, day, FUN = seq_along))
  DF3$diff    <- with(DF3, ave(as.integer(ddate), State, name, day,
FUN = function(x) x - x[1]))

I stopped here, how do I evaluate the previous and the current rows
text string and date difference?

Desired result,


    State name day text      ddate C diff flag
1    CA    A  1  xch 2014-09-16 1    0    y
2    CA    A  2  xck 2015-05-29 1    0      y
3    CA    A  2  xck 2015-06-18 2  20    x
4    CA    A  2  xcm 2015-08-03 3  66    y
5    CA    A  2  xcj 2015-08-26 4  89      y
9    FL    B  3  xca 2017-03-17 1    0      y
10    FL    B  3  xcb 2017-04-08 2  22    y
7    FL    B  3  xcl 2017-07-03 3  108    y
6    FL    B  3  xcu 2017-07-23 4  128    y
8    FL    B  3  xmc 2017-07-26 5  131  y
12    FL    B  4  xhh 2017-01-29 1    0    y
11    FL    B  4  xhh 2017-03-17 2  47    x



Thank you,

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