使用ggplot2复刻Cumulative plot遇问题：按Sample data操作为何出错？

Hey there! Let’s break down the most common reasons your ggplot2 cumulative plot isn’t matching your target—these are the gotchas I’ve stumbled on (and helped others fix) all the time:

• Incorrect cumulative calculation logic

  • Most folks forget to sort their data first, or miscalculate cumulative values across groups. For example, if you’re plotting cumulative values per category, you need to sort your x-axis variable then compute the cumulative sum within each group.
  • Bad example (no grouping/sorting):

    df %>% mutate(cumulative = cumsum(value))
    

  • Good example (sorted + grouped):

    library(dplyr)
    df %>% 
      arrange(x_variable) %>% 
      group_by(category) %>% 
      mutate(cumulative = cumsum(value))
    

• Wrong geom or stat selected

  • Cumulative plots usually use geom_step() (for discrete x-values) or geom_line() (for continuous x). If you’re using geom_bar() (even stacked), it won’t produce the same smooth cumulative trend. Also, stat_ecdf() creates a cumulative distribution function (ranging 0-1), which isn’t the same as plotting raw cumulative counts/values—use this only if your target is a CDF.
  • If your target is raw cumulative totals, skip stat_ecdf(): calculate the cumulative column first, then plot with geom_line() or geom_step().

• Missing or misconfigured grouping

  • If your target plot has multiple cumulative curves (one per group), you need to specify the grouping in your aes() with color = group_var or group = group_var. If you skip this, ggplot will lump all groups together into a single curve. Also, double-check that your grouping variable is the right type (e.g., factor instead of character if needed).
  • Correct grouping example:

    ggplot(df, aes(x = x_variable, y = cumulative, color = category)) + geom_step()
    

• Axis scaling or formatting mismatch

  • Maybe your target plot uses percentages on the y-axis, but your plot shows raw cumulative values (or vice versa). Fix this by converting your cumulative values to percentages (divide by the total sum of your value column) or use scale_y_continuous(labels = scales::percent) to format the axis. Also, ensure your x-axis is sorted correctly—if it’s a categorical or date variable, unsorted values will make your curve jump around.

• Mismatched data structure with the sample

  • The sample data you’re referencing might already be preprocessed (e.g., it has a ready-to-use cumulative column), while you’re working with raw data. Or the sample uses a different grouping strategy, x-axis range, or aggregation level. Double-check that your data matches the sample’s structure before plotting.

If you can share a small snippet of your code and a quick description of what your target plot looks like (e.g., "it’s a step plot of monthly cumulative sales per region, with y-axis from 0 to 10,000"), I can help you pinpoint exactly where things went off! 😊

内容的提问来源于stack exchange，提问作者89_Simple