ggplot2: positioning tick marks on a four quadrant graph along the center axes (ie. x=0, y=0) instead of the border of the plotting area

Question

I am attempting to adjust the position of the tick marks on my plot so they fall along the axis instead of on the perimeter of the plot (which is the default). I have tried using the axis.ticks argument within ggplot2 and this did not work. Here are some example data and the code necessary to produce the graph I am working with:

library(ggplot2)
dat <- data.frame(v1 = c(1, 3, -2, 2, 1, 4, -2, 2),
                  v2 = c(-1, 2, 1, -3, 4, 1, -1, 2))
p = ggplot()
p + geom_point(aes(dat$v1, dat$v2) ,shape = 21, size = 3) + 
  geom_vline(xintercept = 0, linetype = "dashed") +
  geom_hline(yintercept = 0, linetype = "dashed") +
  theme_bw()

Please advise on any packages, functions, or arguments that can be used to move the tick marks onto the axises instead of the outside edges of the graphing area.

Answer 1

Bringing together @user20650's comment linking to Moving x or y axis together with tick labels to the middle of a single ggplot (no facets), which shares @baptiste and @user73708's functions. I removed your dashed lines, and moved the data and aes to the ggplot call.

library(ggplot2)
dat <- data.frame(v1 = c(1, 3, -2, 2, 1, 4, -2, 2),
                  v2 = c(-1, 2, 1, -3, 4, 1, -1, 2))

shift_axis_y <- function(p, y=0){
  g <- ggplotGrob(p)
  dummy <- data.frame(y=y)
  ax <- g[["grobs"]][g$layout$name == "axis-b"][[1]]
  p + annotation_custom(grid::grobTree(ax, vp = grid::viewport(y=1, height=sum(ax$height))), 
                        ymax=y, ymin=y) +
    geom_hline(aes(yintercept=y), data = dummy) +
    theme(axis.text.x = element_blank(), 
          axis.ticks.x=element_blank())
}

shift_axis_x <- function(p, x=0){
      g <- ggplotGrob(p)
      dummy <- data.frame(x=x)
      ax <- g[["grobs"]][g$layout$name == "axis-l"][[1]]
      p + annotation_custom(grid::grobTree(ax, vp = grid::viewport(x=1, width = sum(ax$height))), 
                            xmax=x, xmin=x) +
        geom_vline(aes(xintercept=x), data = dummy) +
        theme(axis.text.y = element_blank(), 
              axis.ticks.y=element_blank())
    }

p <- ggplot(dat, aes(v1, v2)) + 
  geom_point(shape = 21, size = 3) + 
  theme_bw()

p<-shift_axis_y(p, y=0)
p<-shift_axis_x(p, x=0)
p