R语言ggplot中scale_y_log10下设置y轴极值（含0）的方法求助

Hey there! I get why you're frustrated—trying to set a log scale y-axis that includes 0 can feel counterintuitive at first, since log₁₀(0) is mathematically undefined (it's negative infinity). That's exactly why your limits = c(?, ?) parameter wasn't working with scale_y_log10()—ggplot can't handle 0 in a pure log scale.

Here are two solid solutions tailored to your voltage drop plot:

Option 1: Use a Pseudologarithmic Transform (Best for Data Near 0) #

Pseudolog scales act linearly near 0 and switch to logarithmic scaling for larger values, which is perfect for your voltage decay data (where voltage approaches 0 over time). This lets you formally include 0 in your axis limits without mathematical issues.

Modify your code like this:

ggplot(data = rc_data, aes(x = t, y = Vc))+ 
  geom_point()+ 
  geom_smooth(method = lm, se = FALSE) + 
  labs(x = "Time (sec)", y = "Voltage (V), Pseudolog Scale") + 
  ggtitle("Drop of Voltage of a ...") +
  scale_y_continuous(
    trans = "pseudolog10",  # Enables 0-compatible log-like scaling
    limits = c(0, max(rc_data$Vc)),  # Explicitly set 0 as the minimum
    breaks = c(0, 1, 10, 100)  # Adjust these to match your data's range
  )

Option 2: Fake 0 on a Pure Log Scale (If You Need Strict Log Scaling) #

If you absolutely must use a pure log₁₀ scale, you can trick ggplot into displaying 0 by using a tiny positive value as the actual limit, then relabeling it as 0. This works visually, even though the underlying scale doesn't include 0 mathematically.

Try this code:

ggplot(data = rc_data, aes(x = t, y = Vc))+ 
  geom_point()+ 
  geom_smooth(method = lm, se = FALSE) + 
  labs(x = "Time (sec)", y = "Voltage (V), Log Scale") + 
  ggtitle("Drop of Voltage of a ...") +
  scale_y_log10(
    limits = c(1e-6, max(rc_data$Vc)),  # Use a tiny positive value as the lower limit
    expand = expansion(mult = c(0.1, 0.1)),  # Extend axis to visually reach 0
    breaks = c(1e-6, 1e-3, 1, 10, 100),  # Include the tiny value in breaks
    labels = c("0", "0.001", "1", "10", "100")  # Relabel the tiny value as 0
  )

Quick Note on Why Your Original Code Failed #

scale_y_log10() automatically ignores any limit that includes 0 (or negative numbers) because logarithmic transformations can't process non-positive values. The solutions above work around this either by using a transform that handles 0, or by visually mimicking 0 on a valid log scale.

内容的提问来源于stack exchange，提问作者SomebodyNeedingHelp