Hi,
Try this:
dat1 <- read.table(text="
PT_ID IDX_DT OBS_DATE DAYS_DIFF OBS_VALUE CATEGORY
13 4549 2002-08-21 2002-08-20 -1 183 2
14 4549 2002-08-21 2002-11-14 85 91 1
15 4549 2002-08-21 2003-02-18 181 89 1
16 4549 2002-08-21 2003-05-15 267 109 2
17 4549 2002-08-21 2003-12-16 482 96 1
128 4839 2006-11-28 2006-11-28 0 179 2
", header=TRUE)
dat3<-aggregate(DAYS_DIFF~PT_ID,data=dat1,min)
merge(dat1,dat3)
# PT_ID DAYS_DIFF IDX_DT OBS_DATE OBS_VALUE CATEGORY
#1 4549 -1 2002-08-21 2002-08-20 183 2
#2 4839 0 2006-11-28 2006-11-28 179 2
#or,
dat2<- tapply(dat1$DAYS_DIFF,dat1$PT_ID,min)
dat4<-data.frame(PT_ID=row.names(data.frame(dat2)),DAYS_DIFF=dat2)
row.names(dat4)<-1:nrow(dat4)
merge(dat1,dat4)
# PT_ID DAYS_DIFF IDX_DT OBS_DATE OBS_VALUE CATEGORY
#1 4549 -1 2002-08-21 2002-08-20 183 2
#2 4839 0 2006-11-28 2006-11-28 179 2
A.K.
----- Original Message -----
From: WANG WEIJIA <wwang....@gmail.com>
To: "r-help@R-project.org" <r-help@r-project.org>
Cc:
Sent: Saturday, September 1, 2012 1:10 PM
Subject: [R] R_closest date
Hi,
I have encountered an issue about finding a date closest to another date
So this is how the data frame looks like:
PT_ID IDX_DT OBS_DATE DAYS_DIFF OBS_VALUE CATEGORY
13 4549 2002-08-21 2002-08-20 -1 183 2
14 4549 2002-08-21 2002-11-14 85 91 1
15 4549 2002-08-21 2003-02-18 181 89 1
16 4549 2002-08-21 2003-05-15 267 109 2
17 4549 2002-08-21 2003-12-16 482 96 1
128 4839 2006-11-28 2006-11-28 0 179 2
I need to find, the single observation, which has the closest date of
'OBS_DATE' to 'IDX_DT'.
For example, for 'PT_ID' of 4549, I need row 13, of which the OBS_DATE is just
one day away from IDX_DT.
I was thinking about using abs(), and I got this:
baseline<- function(x){
+
+ #remove all uncessary variables
+ baseline<- x[,c("PT_ID","DAYS_DIFF")]
+
+ #get a list of every unique ID
+ uniqueID <- unique(baseline$PT_ID)
+
+ #make a vector that will contain the smallest DAYS_DIFF
+ first <- rep(-99,length(uniqueID))
+
+ i = 1
+ #loop through each unique ID
+ for (PT_ID in uniqueID){
+
+ #for each iteration get the smallest DAYS_DIFF for that ID
+ first[i] <-
min(baseline[which(baseline$PT_ID==PT_ID),abs(baseline$DAYS_DIFF)])
+
+ #up the iteration counter
+ i = i + 1
+
+ }
+ #make a data frame with the lowest DAYS_DIFF and ID
+ newdata <- data.frame(uniqueID,first)
+ names(newdata) <- c("PT_ID","DAYS_DIFF")
+
+ #return the data frame containing the lowest GPI for each ID
+ return(newdata)
+ }
> ldl.b<-baseline(ldl) #get all baseline ldl patient ID, total 11368 obs, all
> unique#
Error in `[.data.frame`(baseline, which(baseline$PT_ID == PT_ID),
abs(baseline$DAYS_DIFF)) :
undefined columns selected
Can anyone help me in figuring out how to get the minimum value of the absolute
value of DAYS_DIFF for unique ID?
Thanks a lot
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and provide commented, minimal, self-contained, reproducible code.
