如何可视化 R 中的多条轨迹？

Question

I am trying to visualize the trajectory of multiple participants in a virtual room using R. I have a participant entering from the right (black square) and moving toward the left, where there is an exit door (red square). Sometimes there is an obstacle right in the middle of the room (circle), and the participant goes around it, moving either to the left of the obstacle (that would be the bottom half of the graph) or to the right of the obstacle (that would be the top half of the graph). In the example below the participant moves to the left of the obstacle to avoid it.

library(shape)
# black line continuous
pos_x <- c(5.04,4.68,4.39,4.09,3.73,3.37,3.07,2.77,2.47,2.11)
pos_z <- c(0.74,0.69,0.64,0.60,0.56,0.52,0.50,0.50,0.50,0.51)
df1 <- cbind.data.frame(pos_x,pos_z)
x.2 <- df1$pos_x
z.2 <- df1$pos_z
plot(x.2,z.2,type="l", xlim=range(x.2), ylim=c(-1,3.5), xlab="x", ylab="z", main = "jagged trajectory using LINES function")
filledrectangle(wx = 0.2, wy = 0.2,col = "black", mid = c(5.16, 1), angle = 0)
filledrectangle(wx = 0.2, wy = 0.2,col = "red", mid = c(2, 1), angle = 0)
plotcircle(mid = c(3.4, 1), r = 0.05)

To visualize multiple participants' trajectories on the same graph (ie, multiple lines), I have used the function plot to set up the plot itself (and the first line) and then I have used the function lines to add other trajectories after that.

This setup usually works pretty well, but I have an issue with the function lines. When a participant crosses the room from the left side of the room to the right or vice versa (that is, goes from the bottom of the graph to the top of the graph, or vice versa) then I have an artifact, a jagged line (see red line below.)

# adding a red line (jagged) to the plot above
pos_x <- c(4.93,4.58,4.29,4.00,3.66,3.52,3.59,3.72,3.76,3.67)
pos_z <- c(0.42,0.33,0.25,0.17,0.20,0.52,0.80,1.14,1.44,1.72)
df2 <- cbind.data.frame(pos_x,pos_z)
x.3 <- df2$pos_x
z.3 <- df2$pos_z
lines(x.3[order(x.3)], z.3[order(x.3)], xlim=range(x.2), ylim=c(-1,3.5), pch=16, col="red")

If I just use just the function "plot" for that single line, then the trajectory would come out right (see red line below.)

# red line continuous
pos_x <- c(4.93,4.58,4.29,4.00,3.66,3.52,3.59,3.72,3.76,3.67)
pos_z <- c(0.42,0.33,0.25,0.17,0.20,0.52,0.80,1.14,1.44,1.72)
df2 <- cbind.data.frame(pos_x,pos_z)
x.3 <- df2$pos_x
z.3 <- df2$pos_z
plot(x.3,z.3,type="l", xlim=range(x.2), ylim=c(-1,3.5), xlab="x", ylab="z",col="red", main = "smooth trajectory using PLOT function")
filledrectangle(wx = 0.2, wy = 0.2,col = "black", mid = c(5.16, 1), angle = 0)
filledrectangle(wx = 0.2, wy = 0.2,col = "red", mid = c(2, 1), angle = 0)
plotcircle(mid = c(3.4, 1), r = 0.05)

I wonder if you think there is a way I could make the line smoother using these functions, by adjusting some parameters, or if should use other functions. I have to say I (still) work mostly in base R when I work with plots, but I welcome solutions in ggplot if needed. Or do you have any other ideas or resources on how to visualize trajectories?

Answer 1

As Allan Cameron noted in the comment, one just needs to simply remove the [order(x.3)] from after x.3 and z.3 in the call to lines :