为tm_symbols设置累计冲突值分级（breaks）失败求助

问题分析 #

从附图可见，当前符号大小的图例显示为连续数值，而非你预期的分级区间，代码无法正常运行的核心原因是**tm_symbols中针对size变量的分级参数用错了**：breaks是给颜色变量（col参数）设置分级的，控制size变量分级的参数是size.breaks。

修正后的代码 #

# 可选：自定义图例区间标签，让展示更清晰
size_labels <- c("<1000", "1000-2000", "2000-3000", "3000-4000", ">4000")

tm_shape(test) + 
  tm_polygons(col="vcidrought_type",
              pal =c("#BCE395","#21908CFF", "#3B528BFF", "#440154FF", "#000004FF"),
              levels = labels,
              title="Drought types") +
  tm_layout(main.title = "VCI drought type in Sub-Saharan Africa 1997-2010", 
            main.title.position = "center", frame= FALSE) +
  tm_shape(shp_union) +
  tm_symbols(col = "red", border.col = "black", size = "total_conflicts",
             size.breaks = c(-Inf, seq(1000, 4000, by = 1000), Inf),
             size.labels = size_labels,  # 启用自定义标签
             title.size = "Cumulated conflicts")

关键说明 #

• 替换breaks为size.breaks，这是tmap中专门控制size变量分级断点的参数；
• 若不需要自定义标签，可删除size.labels行，tmap会自动基于断点生成区间标签；
• 确保size.breaks的断点数量和size.labels的标签数量一致（这里都是5个区间对应5个标签）。

内容的提问来源于stack exchange，提问作者Shunrei