Error in data frame, replacement has xx, data has xx - r

Question

I hope someone can help with this problem - I have been chewing over it for a few hours now!
I have a data frame called 'journeys' as follows which shows a customer ID, their date of travel, mode and journey start time:
ID | Date | Mode | Time
------ | --------- | ------- | -----
1234 | 12/10/16 | Bus | 120
1234 | 12/10/16 | Bus | 130
1234 | 12/10/16 | Bus | 290
1234 | 12/10/16 | Train | 310
1234 | 12/10/16 | Bus | 330
4567 | 12/10/16 | Bus | 220
4567 | 12/10/16 | Tram | 230
4567 | 13/10/16 | Bus | 290
4567 | 13/10/16 | Bus | 450
4567 | 14/10/16 | Train | 1000
So on 12/10, customer 1234 made 4 bus jnys and 1 train jny.
I have written a basic loop in r to create a 5th column which identifies if the journey stages are linked i.e. the 2nd journey linked to the 1st journey, the 3rd journey linked to the 2nd journey (where 1=linked, 0=not linked), based on the following conditions:
the jnys are for the same person and take place on the same day
2 bus journeys/2 tram jnys/a bus and tram jny/a tram and bus jny are within 60 mins of one another (so a bus and train journey within 60 mins of one another would not be linked). The code is as follows:
df <- read.table("Journeys.txt", header=TRUE, sep=",")
for (i in 2:dim(df)[1]) {
if ((df$ID[i]==df$ID[i-1])
& (df$Date[i]==df$Date[i-1])
& ((df$Mode[i]=='Bus' & df$Mode[i-1]=='Bus')|
(df$Mode[i]=='Bus' & df$Mode[i-1]=='Tram')|
(df$Mode[i]=='Tram' & df$Mode[i-1]=='Bus')|
(df$Mode[i]=='Tram' & df$Mode[i-1]=='Tram'))
& (df$Time[i]-df$Time[i-1]<60))
{df$linked[i] <- 1}
else {df$linked[i] <- 0}
This should give me the following output:
ID | Date | Mode | Time | Linked
------ | --------- | ------- | ----- | -----
1234 | 12/10/16 | Bus | 120 | 0
1234 | 12/10/16 | Bus | 130 | 1
1234 | 12/10/16 | Bus | 290 | 0
1234 | 12/10/16 | Train | 310 | 0
1234 | 12/10/16 | Bus | 330 | 0
4567 | 12/10/16 | Bus | 220 | 0
4567 | 12/10/16 | Tram | 230 | 1
4567 | 13/10/16 | Bus | 290 | 0
4567 | 13/10/16 | Bus | 450 | 0
4567 | 14/10/16 | Train | 1000 | 0
However, when I try to run this I keep getting the following error message:
Error in $<-.data.frame(tmp, "linked", value = c(NA, 1)) :
replacement has 2 rows, data has 52231
When I ran this on a test dataset of about 150 rows, I didn't get this error message. I know it's related to the linked column, but I don't fully understand how to resolve it.

Answer 1

I use the same data as you, and it was working with your code (copy paste it) but the first row. you need to initialized it. df$linked[1] <- 0
Here a better use of the if and the condition (faster to read and faster to process for R).
I also add in comment (cat(i)), if you uncomment it, it is helpfull to see what is happening in the loop.
Last thing, I think you are expecting a 0 and not a 1 for the 8th row, as this is not the same day...
df<- read.csv("train.csv", sep=",")
df$linked <- 0
for (i in 2:dim(df)[1]) {
if (df$ID[i]==df$ID[i-1]) {
#cat(i)
if (df$Date[i]==df$Date[i-1]){
#cat(i)
if (df$Time[i]-df$Time[i-1]<60) {
#cat(i)
if (df$Mode[i]=="Bus" & df$Mode[i-1] %in% c("Bus", "Tram")) {
#cat(i)
df$linked[i] <- 1
} else {
if (df$Mode[i]=="Tram" & df$Mode[i-1] %in% c("Bus", "Tram")) {
df$linked[i] <- 1
#cat(i)
}
}
}
}
}
}
ID Date Mode Time linked
1 1234 12/10/2016 Bus 120 0
2 1234 12/10/2016 Bus 130 1
3 1234 12/10/2016 Bus 290 0
4 1234 12/10/2016 Train 310 0
5 1234 12/10/2016 Bus 330 0
6 4567 12/10/2016 Bus 220 0
7 4567 12/10/2016 Tram 230 1
8 4567 13/10/2016 Bus 290 0
9 4567 13/10/2016 Bus 450 0
10 4567 14/10/2016 Train 1000 0