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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.

Rich Pauloo
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Nathan_P_Wilson
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    This isn't, or at least it wasn't, particularly easy to do ... but here are a few links https://stackoverflow.com/questions/39071002/moving-x-or-y-axis-together-with-tick-labels-to-the-middle-of-a-single-ggplot-n, https://stackoverflow.com/questions/20960049/ggplot-and-axis-numbers-and-labels, https://stackoverflow.com/questions/17753101/center-x-and-y-axis-with-ggplot2. As an aside, this is straight forward in base R plots. – user20650 Jun 27 '19 at 22:44
  • No need for `$` inside `aes()`; just `aes(v1, v2)`. – neilfws Jun 27 '19 at 23:15
  • I would argue that the current solution using only `geom_vline` and `geom_hline` works just fine. It indicates x = 0 and y = 0, divides the plot into quadrants and allows rapid inspection of in which quadrant a point lies, without cluttering the body of the plot with ticks and numbers. I suspect that would also be the argument of the `ggplot2` designers. – neilfws Jun 27 '19 at 23:22

1 Answers1

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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
M.Viking
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