ggplot2：如何在刻度线上结束y轴？

Question

我正在使用不同的轴范围制作几个不同的图，所以这个问题不仅适用于我在这里展示的代码。我尝试修改刻度线的间隔和间隔，但是对于某些绘图，y轴始终在最后一次中断后继续。但对于某些人来说，它只是像this一样很好。

这是我目前的情节和代码。我想在60上用刻度线结束y轴：

# Set nucleotide sequence for x-axis labels
my_labs = c("C", "T", "A", "C", "A", "T", "A", "A", "A", "T", "A", "C", "A", "C", "A", "T", "G", "T", "C", "T", "C", "T", "G", "C", "T", "C", "G", "T", "T", "C", "G", "G", "G", "G", "G", "C", "C", "G", "G", "T", "A", "T", "G", "C", "T", "A", "C", "A", "C", "G", "G", "A", "A", "C", "G", "T", "G", "A", "G", "A", "G", "A", "C", "C", "C", "C", "T", "C", "G", "G", "A", "A", "C", "T", "G", "G", "C", "A", "T", "A", "G", "A", "C", "T", "T", "G", "T", "G", "T", "A", "T", "A", "A", "A", "A", "G", "A", "A", "T")

# Set color of each nucleotide
my_cols = c("Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Red", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Blue", "Black", "Black", "Black", "Black", "Black", "Black", "Black", "Black")

ggplot(data = miRNA2) + 
  geom_line(mapping = aes(x = Position, y = CPM), colour="red") +
  scale_y_continuous(breaks = seq(0, 60, 10)) +
  ylab("Counts per million") +
  scale_x_continuous(breaks=1:99, labels=my_labs, expand = c(0, 0)) +
  theme(axis.text.x = element_text(color = my_cols, family = "Courier", size = 6),
        panel.grid.minor.x=element_blank(), panel.grid.major.x=element_blank(), panel.grid.minor.y=element_blank(), panel.background = element_blank(),
        axis.line = element_line(colour = "black")) +
xlab("Supercontig_1.420:40270-40368") +
  ggtitle("Sar-Mir-Nov-2") +
  theme(plot.title = element_text(hjust = 0.5))

Answer 1

只需将limits = c(0,60)和expand = c(0,0)添加到scale_y_continuous：

即可

scale_y_continuous(breaks = seq(0, 60, 10), limits = c(0,60), expand = c(0,0))

Answer 2

您是否要设置ylim max以使显示的最后一个中断舍入到最接近的10？以及所有休息时间以10为增量？

你可以通过抓住gg对象ggplot_build(gg)$layout$panel_ranges[[1]]$y.range的y范围获取ggplot的当前ylim，并将你的ylim max的上限设置为最接近的10，同样设置你的休息时间。这样，您可以根据绘图动态设置限制和中断。

gg <- ggplot(data = miRNA2) + 
  geom_line(mapping = aes(x = Position, y = CPM), colour="red") +
  scale_y_continuous(breaks = seq(0, 60, 10)) +
  ylab("Counts per million") +
  scale_x_continuous(breaks=1:99, labels=my_labs, expand = c(0, 0)) +
  theme(axis.text.x = element_text(color = my_cols, family = "Courier", size = 6), 
  panel.grid.minor.x=element_blank(), panel.grid.major.x=element_blank(),
  panel.grid.minor.y=element_blank(), panel.background = element_blank(),
  axis.line = element_line(colour = "black")) +
  xlab("Supercontig_1.420:40270-40368") +
  ggtitle("Sar-Mir-Nov-2") +
  theme(plot.title = element_text(hjust = 0.5))


# grab y-range of current gg object
ggplot_build(gg)$layout$panel_ranges[[1]]$y.range
gg_ylim_max <- ggplot_build(gg)$layout$panel_ranges[[1]]$y.range[2]

# decide if you want to ceiling to nearest 10's or 5's
library(plyr)
round_any(gg_ylim_max, 10, f = ceiling) # ceiling 10's
round_any(gg_ylim_max, 5, f = ceiling) # ceiling 5's

请试试这个，我没有你的数据，所以我不知道它是否适合你。

gg_ylim_max_round <- round_any(gg_ylim_max, 10, f = ceiling)
gg + scale_y_continuous(breaks = seq(0, gg_ylim_max_round, 10), limits = c(c(0, gg_ylim_max_round)))

编辑了限制的冗余，代码现在应该是正确的。