R语言聚类分析相关性报错求助：correlation对象未找到

我使用《世界幸福报告2022》中的Data_for_Figure_2.1数据集，编写R代码绘制变量相关性热力图，代码如下：

corr <- cor(happy22[, 3:8], method = "pearson")
ggplot(melt(corr, varnames = c("x", "y"), value.name = "correlation"),
aes(x = x, y = y)) +
geom_tile(aes(fill = correlation)) +
scale_fill_gradient2(
low = "green",
mid = "yellow",
high = "red",
guide = guide_colorbar(ticks = FALSE, barheight = 5),
limits = c(-1, 1)
) +
theme(axis.text.x = element_text(angle = 90, hjust = 1)) +
labs(title = "Heatmap of correlation matrix",
x = NULL, y = NULL)

运行后出现错误及警告：

Error in FUN(X[[i]], ...) : object 'correlation' not found
In addition: Warning messages:

    1: In type.convert.default(X[[i]], ...) :
      'as.is' should be specified by the caller; using TRUE
    2: In type.convert.default(X[[i]], ...) :
      'as.is' should be specified by the caller; using TRUE

疑问：为何提示'correlation'未找到？代码中并未出现'as.is'，请求协助解决。

解决方案 #

错误原因解析 #

• 'correlation'未找到：你调用的melt()来自基础R的reshape包，该版本的melt()不支持value.name参数——这个参数是reshape2或data.table包中melt()的特性。基础R的melt()会将值列默认命名为value，而非你指定的correlation，导致ggplot无法识别该变量。
• 'as.is'警告：同样是基础Rmelt()的问题，它在转换数据时会自动调用type.convert()，但未明确指定as.is参数，因此触发警告。

修复后的代码 #

有两种可行方案：

方案1：使用reshape2包的melt函数

先安装并加载reshape2包，再执行代码：

# 首次运行需安装包
install.packages("reshape2")
library(reshape2)

corr <- cor(happy22[, 3:8], method = "pearson")
ggplot(melt(corr, varnames = c("x", "y"), value.name = "correlation"),
       aes(x = x, y = y)) +
  geom_tile(aes(fill = correlation)) +
  scale_fill_gradient2(
    low = "green",
    mid = "yellow",
    high = "red",
    guide = guide_colorbar(ticks = FALSE, barheight = 5),
    limits = c(-1, 1)
  ) +
  theme(axis.text.x = element_text(angle = 90, hjust = 1)) +
  labs(title = "Heatmap of correlation matrix",
       x = NULL, y = NULL)

方案2：使用基础R melt并手动重命名列

如果不想额外安装包，可保留基础R的melt()，手动修改值列名称：

corr <- cor(happy22[, 3:8], method = "pearson")
# 转换格式后重命名第三列为correlation
melted_corr <- melt(corr, varnames = c("x", "y"))
colnames(melted_corr)[3] <- "correlation"

ggplot(melted_corr, aes(x = x, y = y)) +
  geom_tile(aes(fill = correlation)) +
  scale_fill_gradient2(
    low = "green",
    mid = "yellow",
    high = "red",
    guide = guide_colorbar(ticks = FALSE, barheight = 5),
    limits = c(-1, 1)
  ) +
  theme(axis.text.x = element_text(angle = 90, hjust = 1)) +
  labs(title = "Heatmap of correlation matrix",
       x = NULL, y = NULL)

内容的提问来源于stack exchange，提问作者Tianna