将宽数据转换为长数据
1 构建数据框df
x为factor变量，2010和2011位数值变量2. 用reshape2::melt将2维数据转换为一维数据
df_melt<-reshape2::melt(df,id.vars="x",variable.name="year",value.name="value")
Arguments
data | data frame to melt |
|---|---|
id.vars | vector of id variables. Can be integer (variable position) or string (variable name). 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 variables. Can be integer (variable position) or string (variable name)If blank, will use all non id.vars指明测量值列，如果不明确说明，默认出id.var列以外的所有列为measure,上列中就没有明确支出measure.vars,则默认2010和2011均为measure value |
variable.name | name of variable used to store measured variable names 指定measure value的变量名字 |
... | further arguments passed to or from other methods. |
na.rm | Should NA values be removed from the data set? This will convert explicit missings to implicit missings.去除NA值 |
value.name | name of variable used to store values 指定变量值名字 |
factorsAsStrings | Control whether factors are converted to character when melted as measure variables. When FALSE, coercion is forced if levels are not identical across the measure.vars. |
经过melt变换之后的df_melt将长数据转换为宽数据
将上述df_melt转化为宽数据框df
df_cast<-reshape2::dcast(df_melt,x~year,value.var="value")
dcast参数说明
Arguments
formula | casting formula, see details for specifics. |
|---|---|
fun.aggregate | aggregation function needed if variables do not identify a single observation for each output cell. Defaults to length (with a message) if needed but not specified. |
... | further arguments are passed to aggregating function |
margins | vector of variable names (can include "grand_col" and "grand_row") to compute margins for, or TRUE to compute all margins . Any variables that can not be margined over will be silently dropped. |
subset | quoted expression used to subset data prior to reshaping, e.g. subset = .(variable=="length"). |
fill | value with which to fill in structural missings, defaults to value from applying fun.aggregate to 0 length vector |
drop | should missing combinations dropped or kept? |
value.var | name of column which stores values, |
