r - 使用 ggplot2 将 x 轴和 y 轴居中

Question

有没有办法像传统的图形计算器一样获取坐标轴，并将标签放在 ggplot2 图的中心？我浏览了文档，似乎没有这个功能，但其他绘图包不像 ggplot2 那样可以进行图形定制。为了澄清一下，我希望从这样的事情开始:

对此:

第一个图是使用以下代码绘制的:

dat = data.frame(x = 1, y =1)
p = ggplot(data = dat, aes(x=x, y=y)) + geom_point(size = 5)
p + xlim(-2,2) + ylim(-2,2)

第二个图是用 Mathematica 制作的。我遇到的主要问题是弄清楚如何使带有标签的轴到达中心(我可以将主题设为空白等，没问题)。似乎没有可以编辑的主题参数来快速修复此问题。

Answer 1

我认为这就是您正在寻找的:

我已经构建了一个函数来执行此操作:

theme_geometry <- function(xvals, yvals, xgeo = 0, ygeo = 0, 
                           color = "black", size = 1, 
                           xlab = "x", ylab = "y",
                           ticks = 10,
                           textsize = 3,
                           xlimit = max(abs(xvals),abs(yvals)),
                           ylimit = max(abs(yvals),abs(xvals)),
                           epsilon = max(xlimit,ylimit)/50){

  #INPUT:
  #xvals .- Values of x that will be plotted
  #yvals .- Values of y that will be plotted
  #xgeo  .- x intercept value for y axis
  #ygeo  .- y intercept value for x axis
  #color .- Default color for axis
  #size  .- Line size for axis
  #xlab  .- Label for x axis
  #ylab  .- Label for y axis
  #ticks .- Number of ticks to add to plot in each axis
  #textsize .- Size of text for ticks
  #xlimit .- Limit value for x axis 
  #ylimit .- Limit value for y axis
  #epsilon .- Parameter for small space


  #Create axis 
  xaxis <- data.frame(x_ax = c(-xlimit, xlimit), y_ax = rep(ygeo,2))
  yaxis <- data.frame(x_ax = rep(xgeo, 2), y_ax = c(-ylimit, ylimit))

  #Add axis
  theme.list <- 
  list(
    theme_void(), #Empty the current theme
    geom_line(aes(x = x_ax, y = y_ax), color = color, size = size, data = xaxis),
    geom_line(aes(x = x_ax, y = y_ax), color = color, size = size, data = yaxis),
    annotate("text", x = xlimit + 2*epsilon, y = ygeo, label = xlab, size = 2*textsize),
    annotate("text", x = xgeo, y = ylimit + 4*epsilon, label = ylab, size = 2*textsize),
    xlim(-xlimit - 7*epsilon, xlimit + 7*epsilon), #Add limits to make it square
    ylim(-ylimit - 7*epsilon, ylimit + 7*epsilon)  #Add limits to make it square
  )

  #Add ticks programatically
  ticks_x <- round(seq(-xlimit, xlimit, length.out = ticks),2)
  ticks_y <- round(seq(-ylimit, ylimit, length.out = ticks),2)

  #Add ticks of x axis
  nlist <- length(theme.list)
  for (k in 1:ticks){

    #Create data frame for ticks in x axis
    xtick <- data.frame(xt = rep(ticks_x[k], 2), 
                        yt = c(xgeo + epsilon, xgeo - epsilon))

    #Create data frame for ticks in y axis
    ytick <- data.frame(xt = c(ygeo + epsilon, ygeo - epsilon), 
                        yt = rep(ticks_y[k], 2))

    #Add ticks to geom line for x axis
    theme.list[[nlist + 4*k-3]] <- geom_line(aes(x = xt, y = yt), 
                                         data = xtick, size = size, 
                                         color = color)

    #Add labels to the x-ticks
    theme.list[[nlist + 4*k-2]] <- annotate("text", 
                                            x = ticks_x[k], 
                                            y = ygeo - 2.5*epsilon,
                                            size = textsize,
                                            label = paste(ticks_x[k]))


    #Add ticks to geom line for y axis
    theme.list[[nlist + 4*k-1]] <- geom_line(aes(x = xt, y = yt), 
                                             data = ytick, size = size, 
                                             color = color)

    #Add labels to the y-ticks
    theme.list[[nlist + 4*k]] <- annotate("text", 
                                            x = xgeo - 2.5*epsilon, 
                                            y = ticks_y[k],
                                            size = textsize,
                                            label = paste(ticks_y[k]))
  }

  #Add theme
  #theme.list[[3]] <- 
  return(theme.list)
}

作为示例，您可以运行以下代码来创建与上面类似的图像:

simdata <- data.frame(x = rnorm(50), y = rnorm(50))

ggplot(simdata) +
  theme_geometry(simdata$x, simdata$y) +
  geom_point(aes(x = x, y = y), size = 3, color = "red") + 
  ggtitle("More geometric example")

ggsave("Example1.png", width = 10, height = 10)