使用bupaR绘制吞吐量时间图时遇difftime类rescale方法报错

问题重现 #

使用bupaR内置的patients数据集时，以下代码可正常绘制吞吐量时间图：

library(bupaR)

pat <- bupaR::simple_eventlog(eventlog = patients,
                              case_id = ".order",
                              activity_id = "handling_id",
                              timestamp = "time"
)
pat %>%
     throughput_time("case") %>%
     plot()

但使用自定义的po59事件日志执行相同操作时：

po59 <- structure(list(case_id = c("WC4120721", "WC4120667", "WC4120689", 
"WC4121068", "WC4120667", "WC4120666", "WC4120667", "WC4121068", 
"WC4120667", "WC4121068", "WC4121068", "WC4120666", "WC4120721", 
"WC4120666", "WC4120666"), lifecycle = c(110, 110, 110, 110, 
120, 110, 130, 120, 10, 130, 10, 120, 120, 130, 10), action = c("WC4120721-CN354877", 
"WC4120667-CN354878", "WC4120689-CN356752", "WC4121068-CN301950", 
"WC4120667-CSW310", "WC4120666-CN354878", "WC4120667-CSW308", 
"WC4121068-CSW303", "WC4120667-CSW309", "WC4121068-CSW308", "WC4121068-CSW309", 
"WC4120666-CSW310", "WC4120721-CSW310", "WC4120666-CSW308", "WC4120666-CSW309"
), activity = c("Forged Wire, Medium (Sport)", "Forged Wire, Medium (Sport)", 
"Forged Wire, Medium (Sport)", "Forged Wire, Medium (Sport)", 
"BBH-1&2", "Forged Wire, Medium (Sport)", "TCE Cleaning", "SOLO Oil", 
"Tempering", "TCE Cleaning", "Tempering", "BBH-1&2", "BBH-1&2", 
"TCE Cleaning", "Tempering"), resource = c("3419", "3216", "3409", 
"3201", "C3-100", "3216", "C3-080", "C3-030", "C3-090", "C3-080", 
"C3-090", "C3-100", "C3-100", "C3-080", "C3-090"), timestamp = structure(c(-62042010952, 
-62010323872, -61884118792, -61821087232, -61821025132, -61789534972, 
-61789520332, -61789494952, -61757940232, -61757925652, -61757895952, 
-61694827552, -61694808292, -61663337152, -61663307452), tzone = "Europe/Istanbul", class = c("POSIXct", 
"POSIXt")), .order = 1:15), row.names = c(NA, -15L), class = c("eventlog", 
"log", "tbl_df", "tbl", "data.frame"), case_id = "case_id", activity_id = "activity", activity_instance_id = "action", lifecycle_id = "lifecycle", resource_id = "resource", timestamp = "timestamp") 

po59 %>%
          throughput_time("case") %>%
          plot()

会触发以下错误：

Error in UseMethod("rescale") : 
  no applicable method for 'rescale' applied to an object of class "difftime"

问题原因 #

throughput_time("case")针对自定义数据集返回的吞吐量时间是difftime类型，而默认的plot函数尝试对该类型调用rescale方法，但目前没有针对difftime类的rescale实现。而patients数据集的时间计算后会自动转换为数值型（如秒数），因此可以正常绘图。

解决方法 #

方案1：将difftime转换为数值型后绘图 #

把difftime类型转换为具体的数值单位（如天、秒），再调用绘图函数：

library(bupaR)

po59 %>%
  throughput_time("case") %>%
  # 转换为天为单位的数值，也可根据需求选择"secs"/"hours"等单位
  mutate(throughput_time = as.numeric(throughput_time, units = "days")) %>%
  plot()

方案2：手动绘制自定义图形 #

如果需要更灵活的绘图控制，可以用ggplot2手动实现箱线图（和默认plot逻辑一致）：

library(bupaR)
library(ggplot2)

tt_data <- po59 %>%
  throughput_time("case") %>%
  mutate(throughput_time_days = as.numeric(throughput_time, units = "days"))

ggplot(tt_data, aes(x = factor(1), y = throughput_time_days)) +
  geom_boxplot(width = 0.5) +
  labs(title = "Case Throughput Time",
       y = "Throughput Time (days)",
       x = "") +
  theme_minimal()

内容的提问来源于stack exchange，提问作者firmo23