Sorting of data frame per date and string value

Question

I am downloading data from Bloomberg and then update it in R. The dataframe looks as follows.

 ticker       date PX_LAST PE_RATIO
1 SMI Index 2014-09-30 8835.14  20.3692
2 SMI Index 2014-10-31 8837.78  20.3753
3 DAX Index 2014-09-30 9474.30  16.6487
4 DAX Index 2014-10-31 9326.87  16.3896
5 SMI Index 2014-11-28 9150.46  21.0962
6 SMI Index 2014-12-31 8983.37  20.6990
7 DAX Index 2014-11-28 9980.85  17.5388
8 DAX Index 2014-12-31 9805.55  16.8639

Now I would like to have this dataframe sorted according to ticker (not in alphabetical order, but in the order of the ticker) and then the date so that the end result would be:

 ticker       date PX_LAST PE_RATIO
1 SMI Index 2014-09-30 8835.14  20.3692
2 SMI Index 2014-10-31 8837.78  20.3753
3 SMI Index 2014-11-28 9150.46  21.0962
4 SMI Index 2014-12-31 8983.37  20.6990
5 DAX Index 2014-09-30 9474.30  16.6487
6 DAX Index 2014-10-31 9326.87  16.3896
7 DAX Index 2014-11-28 9980.85  17.5388
8 DAX Index 2014-12-31 9805.55  16.8639

Answer 1

There's a function chgroup() in the data.table package that does exactly what you're looking for. It groups values from the vector together while preserving the initial order. It is only available for character vectors (ch for character).

require(data.table)
DF[chgroup(DF$ticker), ]
#     ticker       date PX_LAST PE_RATIO
# 1 SMIIndex 2014-09-30 8835.14  20.3692
# 2 SMIIndex 2014-10-31 8837.78  20.3753
# 5 SMIIndex 2014-11-28 9150.46  21.0962
# 6 SMIIndex 2014-12-31 8983.37  20.6990
# 3 DAXIndex 2014-09-30 9474.30  16.6487
# 4 DAXIndex 2014-10-31 9326.87  16.3896
# 7 DAXIndex 2014-11-28 9980.85  17.5388
# 8 DAXIndex 2014-12-31 9805.55  16.8639

If your ticker column is factor, then convert it first to character type.

Answer 2

You could try order

 df$ticker <- factor(df$ticker, levels=unique(df$ticker))
 df1 <- df[with(df, order(ticker, date)),]
 row.names(df1) <- NULL
 df1
 #     ticker       date PX_LAST PE_RATIO
 #1 SMI Index 2014-09-30 8835.14  20.3692
 #2 SMI Index 2014-10-31 8837.78  20.3753
 #3 SMI Index 2014-11-28 9150.46  21.0962
 #4 SMI Index 2014-12-31 8983.37  20.6990
 #5 DAX Index 2014-09-30 9474.30  16.6487
 #6 DAX Index 2014-10-31 9326.87  16.3896
 #7 DAX Index 2014-11-28 9980.85  17.5388
 #8 DAX Index 2014-12-31 9805.55  16.8639