append list for loop - r

Question

I cannot figure out what i'm doing wrong with appending the results of a loop (as a tibble) into a list.
Below is code. I believe it has to do with the d in distance and the figures not being positive?
Error in datalist[[d]] <- dat :
attempt to select less than one element in integerOneIndex
library(tidyverse)
x <- c(10,5)
y <- c(1,3)
distance <- c(1,2,3) # distance away from the road
old<-data.frame(x,y)
datalist = list()
datalist2 = list()
for (d in 1: length(distance)) {
# Given a vector (defined by 2 points) and the distance,
# calculate a new vector that is distance away from the original
segment.shift <- function(x, y, d){
# calculate vector
v <- c(x[2] - x[1],y[2] - y[1])
# normalize vector
v <- v/sqrt((v[1]**2 + v[2]**2))
# perpendicular unit vector
vnp <- c( -v[2], v[1] )
return(list(x = c( x[1] + d*vnp[1], x[2] + d*vnp[1]),
y = c( y[1] + d*vnp[2], y[2] + d*vnp[2])))
}
# allocate memory for the bike path
xn <- numeric( (length(x) - 1) * 2 )
yn <- numeric( (length(y) - 1) * 2 )
for ( i in 1:(length(x) - 1) ) {
xs <- c(x[i], x[i+1])
ys <- c(y[i], y[i+1])
new.s <- segment.shift( xs, ys, d )
xn[(i-1)*2+1] <- new.s$x[1] ; xn[(i-1)*2+2] <- new.s$x[2]
yn[(i-1)*2+1] <- new.s$y[1] ; yn[(i-1)*2+2] <- new.s$y[2]
}
dat1<-as_tibble()
dat1<-as.data.frame(xn)%>%mutate(id=row_number())%>%mutate(Dist_Col=paste(d,"left",sep="_"))
#datalist[[d]] <- dat1 # add it to your list
dat2<-as_tibble()
dat2<-as.data.frame(yn)%>%mutate(id=row_number())%>%mutate(Dist_Col=paste(d,"left",sep="_"))
#datalist2[[d]] <- dat2 # add it to your list
###Now do right side
# allocate memory for the bike path
xn <- numeric( (length(x) - 1) * 2 )
yn <- numeric( (length(y) - 1) * 2 )
for ( i in 1:(length(x) - 1) ) {
xs <- c(x[i], x[i+1])
ys <- c(y[i], y[i+1])
new.s <- segment.shift( xs, ys, -d )
xn[(i-1)*2+1] <- new.s$x[1] ; xn[(i-1)*2+2] <- new.s$x[2]
yn[(i-1)*2+1] <- new.s$y[1] ; yn[(i-1)*2+2] <- new.s$y[2]
}
dat3<-as_tibble()
dat3<-as.data.frame(xn)%>%mutate(id=row_number())%>%mutate(Dist_Col=paste(d,"right",sep="_"))
datcomb<- full_join(dat1,dat3)
datalist[[d]] <- datcomb # add it to your list
dat4<-as_tibble()
dat4<-as.data.frame(yn)%>%mutate(id=row_number())%>%mutate(Dist_Col=paste(d,"right",sep="_"))
dat2comb<- full_join(dat2,dat4)
datalist2[[d]] <- dat2comb # add it to your list
}
big_data = do.call(rbind, datalist)
big_data2 = do.call(rbind, datalist2)
comb_data<- full_join(big_data,big_data2)
ggplot()+geom_line(data=old,aes(x,y),color='black')+geom_line(data=comb_data,aes(xn,yn,group=Dist_Col),color='red')
see updated code above which plot parallel lines on both sides of the original line.

Answer 1

I resolved the issue finally with
for (d in 1:length(distance))
plot update