R语言绘制分组折线及误差棒时无对应元素的问题求解

• 绘图逻辑不符合需求：现有代码调用的geom_smooth(method = lm)用于生成线性拟合回归线，并非需求要求的「按时间点连接组均值的折线」，也未提前计算误差棒所需的分组统计量，因此不会显示对应元素
• 字段类型与映射缺失：pivot_longer生成的Day字段为字符型，ggplot默认识别为分类变量，绘制折线时未指定group映射，无法按组别完成连线
• 缺少对应绘图图层：代码中未添加折线、误差棒对应的几何对象图层，仅保留了散点图层

library(tidyverse)
library(ggplot2)
theme_set(theme_classic())

# 数据读取与清洗
growth_data <- read.delim("growth_data.txt") %>% tibble()
growth_data_long <- growth_data %>% 
  pivot_longer(-animal, names_to = "Day", values_to = "Growth")
growth2 <- growth_data_long %>%
  mutate(group = str_extract(animal, "\\w+"),
         # 将Day转为数值型，适配时间轴连续展示
         Day = as.numeric(str_extract(Day, "\\d+"))) %>%
  filter(group != "")

# 分组计算统计量，用于绘制均值折线和误差棒
growth_stats <- growth2 %>%
  group_by(group, Day) %>%
  summarise(
    mean_growth = mean(Growth, na.rm = TRUE),
    # 误差棒用标准误，如需标准差可替换为sd(Growth, na.rm = TRUE)
    se = sd(Growth, na.rm = TRUE)/sqrt(n()),
    .groups = "drop"
  )

# 绘图
ggplot() + 
  # 底层绘制原始散点，设置透明度避免遮挡
  geom_point(data = growth2, aes(x = Day, y = Growth, color = group), alpha = 0.4) +
  # 绘制组均值折线
  geom_line(data = growth_stats, aes(x = Day, y = mean_growth, color = group), linewidth = 1) +
  # 绘制误差棒，可自行调整width参数修改误差棒两端横杠宽度
  geom_errorbar(data = growth_stats, 
                aes(x = Day, y = mean_growth, color = group,
                    ymin = mean_growth - se, ymax = mean_growth + se),
                width = 0.2) +
  labs(x = "饲养天数", y = "生长指标", color = "组别")

• 新增了分组统计步骤，计算每个时间点各组的均值和标准误，作为折线和误差棒的绘制基础
• 将Day字段从字符型转为数值型，更符合生长趋势的连续时间展示逻辑
• 分层添加散点、折线、误差棒图层，可根据需求调整各图层的样式参数（颜色、线宽、透明度等）
• 误差棒默认使用标准误，如需展示标准差可替换summarise中se的计算逻辑

内容的提问来源于stack exchange，提问作者angel_30