Parabolic reference lines on ggplot

Question

I am moving my plots into ggplot. Almost there except for this one (code got from this previous question): ``` #Set the bet sequence and the % lines betseq <- 0:700 #0 to 700 bets perlin <- 0.05 #Show the +/- 5% lines on the graph #Define a function that plots the upper and lower % limit lines dralim <- function(stax, endx, perlin) { lines(stax:endx, qnorm(1-perlin)*sqrt((stax:endx)-stax)) lines(stax:endx, qnorm(perlin)*sqrt((stax:endx)-stax)) } #Build the plot area and draw the vertical dashed lines plot(betseq, rep(0, length(betseq)), type="l", ylim=c(-50, 50), main="", xlab="Trial Number", ylab="Cumulative Hits") abline(h=0) abline(v=35, lty="dashed") #Seg 1 abline(v=185, lty="dashed") #Seg 2 abline(v=385, lty="dashed") #Seg 3 abline(v=485, lty="dashed") #Seg 4 abline(v=585, lty="dashed") #Seg 5 #Draw the % limit lines that correspond to the vertical dashed lines by calling the #new function dralim. dralim(0, 35, perlin) #Seg 1 dralim(36, 185, perlin) #Seg 2 dralim(186, 385, perlin…

Accepted Answer

What you were doing was fitting a parabola to your data, not drawing a previously defined parabola. It's not too hard to adapt what you had to `ggplot`.

Same start as you had (though `betseq` is not actually used anywhere)

```
#Set the bet sequence and the % lines
betseq <- 0:700 #0 to 700 bets
perlin <- 0.05 #Show the +/- 5% lines on the graph
```

Not instead of a function which draws lines, make a function which returns `geom_line`s (in a list) that are what you want. There is an implied `aes(x=x, y=y)` which will be given in the `ggplot` declaration later, but this defines the data points that make the parabolas.

```
#Define a function that plots the upper and lower % limit lines
dralim <- function(stax, endx, perlin) {
  c(geom_line(data = data.frame(x=stax:endx, 
                                y=qnorm(1-perlin)*sqrt((stax:endx)-stax))),
    geom_line(data = data.frame(x=stax:endx, 
                                y=qnorm(perlin)*sqrt((stax:endx)-stax))))
}
```

To save repetition, define the position of the vertical lines (`edges`), which also can be used to define the left and right endpoints of the parabolas (`ranges`).

```
edges <- data.frame(x=c(0, 35, 185, 285, 485, 585, 700))
ranges <- data.frame(left = edges$x[-nrow(edges)],
                     right = edges$x[-1] + 1)
```

Now build the `ggplot`. There a single `geom_vline` to draw all the vertical lines (since we defined the positions in a single dataset). The unusual step is looping over the row (indices) of `ranges` and calling `dralim` with the corresponding left and right values (and `perlin`). This returns a list of lists of `geom_lines`, but that can just be added to a plot in the normal way and all the lines get added. The final two scale calls are just to set the labels and, in the case of the y axis, range.

```
ggplot(mapping=aes(x=x,  y=y)) +
  geom_vline(data=edges, aes(xintercept = x), linetype="dashed") +
  lapply(seq_len(nrow(ranges)), 
         function(r) {dralim(ranges$left[r], ranges$right[r], perlin)}) +
  scale_y_continuous("Cumulative Hits", lim=c(-50,50)) +
  scale_x_continuous("Trial Number")
```

Parabolic reference lines on ggplot

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