英文:
Using ggplot2 and a secondary y-axis, how can I plot a log10 scale on the left y-axis and a linear scale on the right?
问题
这让我感到疯狂，主要是因为我以前做过，但找不到相关代码。
假设我有以下数据框：
df <- tibble(
时间 = 0:19,
VAL1 = seq(from = 10, to = 2500, length.out = 20),
VAL2 = seq(from = 1, to = 30, length.out = 20))
我想绘制具有较大范围的VAL1，使用对数刻度在左y轴上绘制，并且绘制具有较小范围的VAL2，使用线性刻度在右y轴上绘制。
我知道有其他示例（请参见这里和这里），但似乎无法使用这些方法正确对齐y轴。
有什么想法？
英文:
This is driving me crazy, mostly because I've done it before and can't find the code for it.
Let's say I have the following dataframe:
df <- tibble(
TIME = 0:19,
VAL1 = seq(from = 10, to = 2500, length.out = 20),
VAL2 = seq(from = 1, to = 30, length.out = 20))
I'd like VAL1, which has a large range, to be plotted on the left y-axis using a log scale, and VAL2, which has a much smaller range, to be plotted on the right y-axis using a linear scale.
I know there are other examples out there (see here and here), but I can't seem to get the y-axes to line up correctly using those approaches.
Any thoughts?
答案1
得分: 1
ggplot2的次要坐标轴必须是主要坐标轴的线性变换。因此，我们可以将VAL1转换为其对数，以便将两个系列都映射到线性刻度上。（需要一些标签使主要坐标轴的级别显示为指数。）
在这里，我将VAL2除以12，然后加1，以使其覆盖与VAL1的log10类似的范围。次要坐标轴的标签需要相反操作，先减去1，然后乘以12。
ggplot(df, aes(TIME)) +
geom_line(aes(y = log10(VAL1), color = "VAL1")) +
geom_line(aes(y = VAL2/12 + 1, color = "VAL2")) +
scale_y_continuous(
labels = function(x) scales::comma(round(10^x), accuracy = 1),
breaks = c(0:10, 0:10 + 0.3979, 0:10 + 0.69897),
minor_breaks = NULL,
sec.axis = sec_axis(~(.-1)*12))
英文:
ggplot2's secondary axes have to be a linear transformation of the primary axis. So we can convert VAL1 to its log so that both series can be mapped to a linear scale. (With some labeling to make the primary axis levels show exponentials.)
Here, I divide VAL2 by 12 and add one to make it cover similar range as the log10 of VAL1. The secondary axis labeling needs to the reverse, subtracting 1 and then multiplying by 12.
ggplot(df, aes(TIME)) +
geom_line(aes(y = log10(VAL1), color = "VAL1")) +
geom_line(aes(y = VAL2/12 + 1, color = "VAL2")) +
scale_y_continuous(
labels = function(x) scales::comma(round(10^x), accuracy = 1),
breaks = c(0:10, 0:10 + 0.3979, 0:10 + 0.69897),
minor_breaks = NULL,
sec.axis = sec_axis(~(.-1)*12))
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