在R中对数据框的特定行进行排序

Question

Data:-

df:-

    Name       Date
1    A     2015-01-01
2    B     2016-05-01
3    B     2015-01-05
4    A     2015-12-25
5    C     2015-01-01

Code:-

df <- df[order(df[,c("Name")]),]
> df
  Name       Date
1    A 2015-01-01
4    A 2015-12-25
2    B 2016-05-01
3    B 2015-01-05
5    C 2015-01-01
index= which(df$Name=="B")
start= index[1]
end=index[length(index)]
df[start:end,] <- df[order(df[start:end,("Date")]),]

> df
   Name       Date
1    A    2015-01-01
4    A    2015-12-25
2    A    2015-12-25
3    A    2015-01-01
5    C    2015-01-01

As one can see this is not the output I was expecting. I sort the dataframe first by Name ,which works well and then I try to sort the individual rows of specific names. I find the starting and ending index of a particular name and try to sort the specific rows by Date . Second sorting leads to this error output. Please advice , also is there any shorter method for this? Thanks in advance.

Expected Output:-

Name       Date
1    A 2015-01-01
4    A 2015-12-25
3    B 2015-01-05 
2    B 2016-05-01
5    C 2015-01-01

Answer 1

It appears that you do not yet understand that order can take both primary and secondary sort vectors:

> df1 <- read.table(text="    Name       Date
+ 1    A     2015-01-01
+ 2    B     2016-05-01
+ 3    B     2015-01-05
+ 4    A     2015-12-25
+ 5    C     2015-01-01", head=TRUE)
> df1[ order(df1$Name, df1$Date) , ]
  Name       Date
1    A 2015-01-01
4    A 2015-12-25
3    B 2015-01-05
2    B 2016-05-01
5    C 2015-01-01