涉及多数据集的ggplot图表如何添加区分各资产对应颜色的图例

你当前的代码没有生成图例，是因为color参数写在了aes()映射之外，属于手动指定固定颜色，ggplot2不会将这类独立设置的样式纳入图例生成逻辑。你可以选择以下两种方案解决：

方案1：优先推荐（符合ggplot2语法规范） #

先将多个资产的数据集合并为统一长表，再通过变量映射生成图例，后续维护更方便：

1. 合并数据集

library(dplyr)
library(ggplot2)

# 为每个资产数据集添加标识列
Polkadot <- Polkadot %>% mutate(Asset = "Polkadot")
Cardano <- Cardano %>% mutate(Asset = "Cardano")
Solana <- Solana %>% mutate(Asset = "Solana")
Tezos <- Tezos %>% mutate(Asset = "Tezos")
Bitcoin <- Bitcoin %>% mutate(Asset = "Bitcoin")
Basket <- Basket %>% mutate(Asset = "Basket")

# 纵向合并所有数据
all_assets <- bind_rows(Polkadot, Cardano, Solana, Tezos, Bitcoin, Basket)

2. 绘图代码

ggplot(all_assets, aes(x = Date, y = Price.Last, color = Asset)) +
  geom_line(size = 1.5) +
  # 匹配你原本设定的颜色对应关系
  scale_color_manual(values = c(
    "Polkadot" = "blue",
    "Cardano" = "blue4",
    "Solana" = "cyan",
    "Tezos" = "cyan4",
    "Bitcoin" = "black",
    "Basket" = "deepskyblue"
  )) +
  theme_bw()

方案2：无需调整现有数据结构 #

直接在每个geom_line的aes()内定义颜色映射，手动绑定颜色和资产的对应关系：

ggplot() + 
  geom_line(data = Polkadot, aes(x=Date, y=Price.Last, color="Polkadot"), size=1.5) + 
  geom_line(data = Cardano, aes(x=Date, y=Price.Last, color="Cardano"), size=1.5) +
  geom_line(data = Solana, aes(x=Date, y=Price.Last, color="Solana"), size=1.5) +
  geom_line(data = Tezos, aes(x=Date, y=Price.Last, color="Tezos"), size=1.5) +
  geom_line(data = Bitcoin, aes(x=Date, y=Price.Last, color="Bitcoin"), size=1.5) +
  geom_line(data = Basket, aes(x=Date, y=Price.Last, color="Basket"), size=1.5) +
  # 自定义图例名称和颜色映射
  scale_color_manual(name = "资产名称", values = c(
    "Polkadot" = "blue",
    "Cardano" = "blue4",
    "Solana" = "cyan",
    "Tezos" = "cyan4",
    "Bitcoin" = "black",
    "Basket" = "deepskyblue"
  )) +
  theme_bw()

内容的提问来源于stack exchange，提问作者marco