Using R, how to create a new data set with the Median of a column in my existing dataframe?

Question

I am new to R and I want a new data set from my dataframe that will include a new column which represents the median of the values in an existing column (called Total Extras) of the dataframe. The latter consists of around 5,000 individual observations. I am a bit confused on how to proceed with this task as the Median need to be calculated based on the following criteria: Property, Month, Year and Market

Currently, my dataframe (let's call it mydata1) stands as follows (first 5 rows shown):

Property    Date      Month  Year      Market    TotalExtras
ZIL         1-Jan-15    1    2015        UK         450.00
ZIL         1-Jan-15    1    2015        UK         125.00
ZIL         1-Feb-15    2    2015        UK         300.00
ZIL         1-Feb-16    2    2016        FR         225.00
EBA         1-Feb-15    2    2015        UK         150.00
... 

I need my R codes to create a new dataframe (let's call it mydata2) to appear like below:

   Property        Date      Month  Year      Market    MedianTotalExtras
     ZIL         1-Jan-15      1    2015        UK         175.00
     ZIL         1-Feb-15      2    2015        UK         250.00
     ZIL         1-Feb-16      2    2016        FR         400.00
     EBA         1-Feb-15      2    2015        UK         328.00
     ...

The figures above are for illustration purposes only. Basically, mydata2 is re-grouping the data based on Property, Date and Market with the column 'Median Total Extras' replacing the 'TotalExtras' column of mydata1.

Can this be done with R?

Answer 1

In dplyr the general gist will be something like:

mydata1 %>% 
    group_by(Property, Date, Market) %>% 
    summarise(MedianTotalExtras = median(TotalExtras))

where group_by arranges the cutting up of the dataset into pieces with unique Property, Date, Market combos, and the summarise + median calculates the median.