ggplot 轴缩放

Question

以下脚本用于在一个公共 x 轴和两个明显缩放的 y 轴上绘制数据：

scale <- max(data$one) / max(data$two)
#See 

ggplot(data3, aes(x=time)) +
  labs(title = "Title", x="Time") +
  geom_line(aes(x=time, y=one, col="cf_media")) +
  geom_line(aes(x=time, y=two * scale, col="two")) + 
  scale_x_date(breaks=scales::pretty_breaks(n = 6), expand = c(0,0)) + 
  scale_color_manual(values = c("red", "blue")) +
  scale_y_continuous(name="Left Axis",
                     sec.axis=sec_axis(~./scale, 
                                       breaks = scales::pretty_breaks(n = 6),
                                       name="Right Axis"),
                     minor_breaks=NULL,
                     breaks = scales::pretty_breaks(n = 6)) +
  theme(legend.position = c(.90, .95),
        legend.title=element_blank())

输出：

此图的问题在于，由于某种原因，左轴（红线）未正确缩放。最小轴值远低于真实最小值。在 20 张图表中，这是唯一一张似乎有此错误的图表。右轴（蓝色）看起来还不错。

问题：用两个不同的 y 轴适当绘制这两个时间序列的最佳方法是什么，可能不添加 limits=？

数据粘贴在下面。

感谢您的帮助！

dput(数据):

structure(list(time = structure(c(15431, 15461, 15492, 15522, 
15553, 15584, 15614, 15645, 15675, 15706, 15737, 15765, 15796, 
15826, 15857, 15887, 15918, 15949, 15979, 16010, 16040, 16071, 
16102, 16130, 16161, 16191, 16222, 16252, 16283, 16314, 16344, 
16375, 16405, 16436, 16467, 16495, 16526, 16556, 16587, 16617, 
16648, 16679, 16709, 16740, 16770, 16801, 16832, 16861), class = "Date"), 
    one = c(18.4221796200761, 18.3967231898903, 16.335633117503, 
    16.730296027773, 18.1514409360143, 17.7199441162588, 16.799170250284, 
    15.4179238554614, 17.4392839966129, 17.595792430154, 16.9553497988467, 
    16.4953670246957, 17.5849417055811, 17.9678266256, 17.1739918955819, 
    17.6002431353711, 17.9595179193721, 17.999935039935, 17.7524652108263, 
    17.7177489902007, 17.3588650113878, 17.6725182139017, 17.4405657957642, 
    17.6704974950091, 17.8875447511326, 16.9658703405016, 17.4780706514254, 
    18.1277851044477, 18.1761216072241, 17.1620759199987, 18.4686443856938, 
    18.5762732410043, 17.4880377648686, 17.829055609543, 18.3096877847122, 
    16.9076887297865, 17.8248723024602, 17.9126225373526, 17.6292589941241, 
    18.5179618982914, 18.5366398684046, 18.0677764393526, 16.6418177564593, 
    16.9211415340111, 17.9654709207359, 17.6361844282822, 18.2270338206168, 
    16.4429651207772), two = c(16.6582662387643, 16.6291067627203, 
    16.6371145606996, 16.4961540261816, 17.0596826781454, 16.7062765725755, 
    16.7162150801773, 16.5497433654548, 16.289748798776, 16.2175637229181, 
    16.2087465723472, 16.7917693011438, 17.0844034991311, 17.1252018488917, 
    17.035226133743, 16.7162471713475, 16.7691021105687, 16.2972221957997, 
    16.708788985733, 16.7827078467867, 16.4754347061264, 16.0403929689546, 
    16.2594260331233, 16.6004611360169, 16.6892567341726, 16.7962173532738, 
    16.4205670536356, 16.9984920528234, 16.3600444060327, 16.2367171945242, 
    16.5735658839198, 16.5205739998051, 16.483858284178, 15.7240973247951, 
    17.0266878151606, 16.9142806023417, 16.788529867979, 16.5935730790947, 
    16.424863694705, 17.0269967594955, 16.3278055932357, 16.3832866771369, 
    16.6118799527132, 16.8515435281064, 16.8155186621117, 15.5626066989097, 
    16.2053235276769, 16.9638862520006)), .Names = c("time", 
"one", "two"), row.names = c(NA, 48L), class = "data.frame")

Answer 1

如果我理解正确，OP 想要缩放第二个时间序列 two 以便缩放后的值与时间序列 one.[=22= 的值位于相同的区间内]

为此，我们需要缩放范围并考虑偏移量，即

一个 = scl * 两个 + ofs

scl和ofs的值可以由one和two的min()和max()值确定，分别.:

scl <- (max(dat$one) - min(dat$one)) / (max(dat$two) - min(dat$two))
ofs <- min(dat$one) - scl * min(dat$two)

library(ggplot2)
ggplot(dat, aes(x = time)) +
  labs(title = "Title", x = "Time") +
  geom_line(aes(x = time, y = one, col = "one")) +
  geom_line(aes(x = time, y = two * scale + ofs, col = "two")) +
  scale_x_date(breaks = scales::pretty_breaks(n = 6), expand = c(0, 0)) +
  scale_color_manual(values = c("red", "blue")) +
  scale_y_continuous(
    name = "Left Axis",
    sec.axis = sec_axis(~ (. - ofs) / scl, 
                        name = "Right Axis"),
    minor_breaks = NULL,
    breaks = scales::pretty_breaks(n = 6)) +
  theme(legend.position = c(.90, .95),
        legend.title = element_blank())

现在，两个时间序列的最小值和最大值分别绘制在相同的 y 值上。

请注意左边的刻度属于时间序列one（红线），右边的刻度属于时间序列two（蓝线）。

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