拼写错误，首行导入时把导入的包重命名为detasets，而第三行使用时缺写成datasets，首行拼写错误，应写为dataset
R语言dataframe数据转换 用reshape2::melt将2维数据转换为一维数据 df_meltname="year",value.name="value...If blank, will use all non-measured variables.指明分组变量,该列为原来df的factor列 measure.vars vector of measured...Can be integer (variable position) or string (variable name)If blank, ...