如何在 X 轴上获得具有相等间隔的日期范围的直方图？

Question

I have a dataframe which is something like this -

col_1 | col_2 | col_3 | col_4
-----------------------------
  A   |  11   | 4/12/2017 | "aaa"
  B   |  22   | 4/04/2003 | "bbb"
  C   |  98   | 4/11/1905 | "ccc"
....  ...  ... ... ... ... ..
....  ...  ... ... ... ... ..
....  ...  ... ... ... ... ..
  Y   |  101  | 8/12/1950 | "ddd"

I am trying to draw an histogram plot with range of years in the X axis and frequency in the Y axis.

For example -

If I pass, year = 5, as the argument to my function(which would draw the plot), it should create the histogram with frequency of values between [starting_date(of col_3),starting_date + 5years] as the first bar, then the last date + 5 years, and so on till the last date is reached.

Each bar should have the values falling in that range of dates.

My approach -

I have tried to use pd.interval_range + pd.cut but it didn't seem to work for me.

interval = pd.interval_range(start=df["Resignation Date"].min(),end=df["Resignation Date"].max(),freq='5Y')
pd.cut(df['Resignation Date'], bins=interval) <-- This doesn't create intervals of 5 years range

When I try to plot the above, it says, TypeError: no numeric data to plot

Any help appreciated.

Answer 1

One approach is to convert the datetime objects in the "Resignation Date" column to numbers, using matplotlib's date_2_num method. The number of bins can then be calculated by (max-min)/(365*years_interval) as shown in the function below:

def plot_histogram(df_date_column, years_interval):
    dates_as_numbers = date2num(df_date_column)
    days_interval = years_interval * 365
    num_bins = round((dates_as_numbers.max() - dates_as_numbers.min()) / days_interval)

    plt.hist(df_date_column, bins=num_bins, ec = 'k')
    plt.gcf().autofmt_xdate()
    plt.xlabel('Year')
    plt.ylabel('Count')
    plt.show()

As an example, for the following dataframe, the function produces the following plot:

             Country       Date     Profit
0       South Africa 2012-07-28    3839.13
1            Morocco 2013-10-19  338631.84
2   Papua New Guinea 2015-06-04   20592.00
3           Djibouti 2017-07-02   41273.28
4           Slovakia 2016-12-04   62217.18
..               ...        ...        ...
95           Liberia 2015-06-12  126918.64
96      Turkmenistan 2017-05-14  297783.20
97            Malawi 2016-03-12  291376.80
98           Vanuatu 2014-08-05  503279.79
99              Mali 2015-12-07  353819.26

plot_histogram(df['Date'], years_interval=2)