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Ylim() function

As explained in Statistics Slam Dunk

The ylim() function specifies or constrains the y-axis limits of a plot.

In ggplot2, ylim() specifies the visible range of a plot’s y-axis. It is especially useful when comparing charts: applying the same limits prevents differing scales from making equal-sized bars appear misleadingly different. section 2.5.5

Use ylim() to control the vertical space available for bars and labels:

  • Write ylim(lower, upper), such as ylim(0, 35), to standardize two win-share bar charts. section 2.5.5
  • Choose an upper limit that leaves room for geom_text() labels placed above the bars. section 14.3
  • Remember that axis choices affect visual comparison: unequal scales can conceal differences between means and medians. section 2.5.5

Compare average and median career win shares

p5 <- ggplot(tenth_tibble, aes(x = Born2, y = meanWS)) + geom_bar(stat = "identity") + geom_text(aes(label = trunc(meanWS), vjust = -0.3)) + ylim(0, 35) p6 <- ggplot(tenth_tibble, aes(x = Born2, y = medianWS)) + geom_bar(stat = "identity") + geom_text(aes(label = trunc(medianWS), vjust = -0.3)) + ylim(0, 35) p5 + p6 + plot_layout(ncol = 2) Both charts now use the same vertical scale, making the differences between average and median win shares easier to judge. section 2.5.5

p5 <- ggplot(tenth_tibble, aes(x = Born2, y = meanWS)) + 
 geom_bar(stat = "identity", width = .5, fill  = "darkorchid4") + 
 labs(title = "Average Win Shares by Place of Birth",
      subtitle = "2000-09 NBA Drafts", 
      x = "Where Born", 
      y = "Average Career Win Shares") + 
 geom_text(aes(label = trunc(meanWS), vjust = -0.3)) +
 ylim(0, 35) +
 theme(plot.title = element_text(face = "bold"))

p6 <- ggplot(tenth_tibble, aes(x = Born2, y = medianWS)) + 
 geom_bar(stat = "identity", width = .5, fill  = "sienna1") + 
 labs(title = "Median Win Shares by Place of Birth",
      subtitle = "2000-09 NBA Drafts", 
      x = "Where Born", 
      y = "Median Career Win Shares") + 
 geom_text(aes(label = trunc(medianWS), vjust = -0.3)) +
 ylim(0, 35) +
 theme(plot.title = element_text(face = "bold"))

Inspect the complete ggplot2 code for two NBA win-share bar charts using ylim(0, 35), text labels, and matching styling. section 2.5.5

How Statistics Slam Dunk covers it

How deep it goes
Demonstrates explicit lower and upper limits in bar charts, stopping short of broader scale customization.
Examples
Uses NBA career win-share means and medians, plus seasonal average points scored per game.
What it assumes
Assumes familiarity with ggplot2 bar charts, aesthetic mappings, and geom_text() annotations.
What you can do after
Apply it via ggplot2 to align comparable y-axis scales and create space for annotations.
How it connects
Connects y-axis limits with ggplot2, geom_bar(), geom_text(), and patchwork plot comparison.
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Related concepts

This explainer was generated by Manning's knowledge graph from the text of Statistics Slam Dunk. The section links point to the parts of the book it draws on.