ggplot2 2D 密度图 - 渐变填充太平滑

I am having some difficulty with the ggplot2 package and the gradient fill. For my data with low number of data points, its gradient and density intensity doesn't really match. Here is an example:

我正在使用的代码是：

pt <- read.xlsx("plots.xlsx", sheetName = "PT1_TB varseq", stringsAsFactors=FALSE)

ggplot(pt, aes(x=pt$BAF, y=pt$LogR) ) + 
  stat_density_2d(aes(fill = ..density..), geom = "raster", contour = FALSE) +
  scale_fill_distiller(palette= "Spectral", direction=-1) +
  scale_y_continuous(name="LogR", limits = c(-0.8, 0.6), breaks = seq(-0.8, 0.6, 0.2)) +
  scale_x_continuous(name="BAF", breaks = seq(0, 0.8, 0.2)) +
  theme(
    legend.position='none',
    panel.grid.major = element_blank(),
    panel.grid.minor = element_blank(),
    panel.background = element_blank(),
    axis.line = element_line(colour = "black")
  ) +
  geom_point(aes(shape = factor("cyl")), size = 1) + scale_shape(solid = FALSE)

我希望渐变变化得更突然，例如，我希望看到 (0;0.2) 和 (0.25;-0.2) 点之间的颜色有更多分离。此外，中间没有点的黄色应该是蓝色的。

当我这样做时，有人知道如何消除轴和实际绘图之间的白色间隙吗？

提前致谢 ：）

如果您能提供一个可重现的示例，将会有所帮助。然而，为了阐明 @RichardTelford home 评论中的观点，这里有一个利用manipulate包以交互方式设置h带宽参数，除了n-- 网格点数。

library(ggplot2)
library(manipulate)

manipulate(
  ggplot(faithful, aes(x = eruptions, y = waiting)) +
    geom_point() +
    xlim(0.5, 6) +
    ylim(40, 110) +
    stat_density_2d(geom = "raster", aes(fill = ..density..), contour = F, 
                    h = c(x_bandwidth, y_bandwidth),
                    n = grid_points) +
    scale_fill_distiller(palette = "Spectral", direction = -1),
  x_bandwidth = slider(0.1, 20, 1, step = 0.1),
  y_bandwidth = slider(0.1, 20, 1, step = 0.1),
  grid_points = slider(1, 100, 16)
)

所以我们的普通（默认）图如下所示：

我们可以使用齿轮图标访问的弹出菜单以交互方式更改参数：