R:我如何检查不同列的增加/减少值

Question

如何查看学生在"二年级"是否取得了更高的分数?与他们之前在"一年级"的成绩相比

df = data.frame(Grade1 = c("5","1","7","6"), 
Grade2 = c("4", "5", "10", "10"))
df
rownames(df) = c("StudentA","StudentB","StudentC","StudentD")
df

Answer 1

确保您的数据框架包含整数而不是字符串。

df = data.frame(Grade1 = c(5,1,7,6), 
Grade2 = c(4, 5, 10, 10))
rownames(df) = c("StudentA","StudentB","StudentC","StudentD")
mask <- df$Grade2 > df$Grade1
rownames(df[mask,])

输出:

[1] "StudentB" "StudentC" "StudentD"