6.5. Comparing forms of Government

The goal of this section is to be able to do some comparison of the different forms of government and how the form of government might have an impact some of our other variables. We’ll do this by building a pivot table in Pandas. You have done this in a spreadsheet, so its good to see how to do it in Pandas as well. In order to accomplish this we are going to have to do the following:

  1. Learn or review how you can do some screen scraping to get the form of government.
  2. Learn about the pivot_table and pivot methods
  3. Practice adding new data to a data frame.

If you haven’t already you should review the example of Challenge: Screen Scraping the CIA. This will show you the basics of reading and grabbing information out of a page. when you are comfortable with that you can dig in to getting the information from this page

Now Lets look at making a pivot table. We will leave pivoting on the form of government up to you. Instead, we will do an example to see how climate the region of the world, and parts of the economy might be related. We have a column for region, we have a column for climate, and we have information on the economy. What we want to do is summarize that information in a table where we have a row for each region, and a column for each classification of climate. Then in each cell we would like to summarize the fraction of the economy that comes from agriculture.

Climate 1.0 1.5 2.0 2.5 3.0 4.0
ASIA (EX. NEAR EAST) 0.229500 0.1250 0.167500 0.186 0.116667 NaN
BALTICS NaN NaN NaN NaN 0.040000 NaN
C.W. OF IND. STATES 0.230667 NaN 0.234000 0.353 0.179500 0.133
EASTERN EUROPE NaN NaN NaN NaN 0.087500 0.142
LATIN AMER. & CARIB NaN 0.0820 0.094722 NaN 0.082667 NaN
NEAR EAST 0.060100 NaN NaN NaN 0.060000 NaN
NORTHERN AFRICA 0.125000 NaN NaN NaN 0.132000 NaN
NORTHERN AMERICA NaN NaN 0.010000 NaN 0.010000 NaN
OCEANIA 0.038000 NaN 0.194357 NaN 0.043000 NaN
SUB-SAHARAN AFRICA 0.230714 0.2455 0.311406 0.119 0.228333 NaN
WESTERN EUROPE NaN NaN NaN NaN 0.029389 0.041

OK, the first thing we really want to do is change those headings. climate values of 1.0, 2.0 etc are not very useful. But we can translate that into more human friendly form.

The Climate numbers are as follows:

1. Dry tropical or Tundra 1.5 Mixed tropical 2. Wet tropical 2.5 Mixed 3. Temperate 4. Dry summers and wet winters.

Lets change our climate classification from numeric to nominal. We can do this using the map method, a lambda function, and a dictionary that maps from the climate number to a label.

Now lets pivot the table. The pivot table method takes three parameters: index, columns, and values. The index parameter says “What values from the original table should I use as the new row index?” The columns parameter asks “what values from the original table should I use as the column headings?”, and the values parameter says what values to include in the cells. In most cases these values will need to be aggregated in some way, and by default the aggregation is to take the mean.

wd.pivot_table(index='Region', columns='Climate', values='Agriculture')
Climate Dry Tropical or Tundra Mixed Mixed Tropical Mountain Temperate Unknown Wet Tropical
ASIA (EX. NEAR EAST) 0.229500 0.186 0.1250 NaN 0.116667 0.3800 0.167500
BALTICS NaN NaN NaN NaN 0.040000 0.0550 NaN
C.W. OF IND. STATES 0.230667 0.353 NaN 0.133 0.179500 0.1335 0.234000
EASTERN EUROPE NaN NaN NaN 0.142 0.087500 0.0880 NaN
LATIN AMER. & CARIB NaN NaN 0.0820 NaN 0.082667 NaN 0.094722
NEAR EAST 0.060100 NaN NaN NaN 0.060000 0.1200 NaN
NORTHERN AFRICA 0.125000 NaN NaN NaN 0.132000 0.1465 NaN
NORTHERN AMERICA NaN NaN NaN NaN 0.010000 0.0220 0.010000
OCEANIA 0.038000 NaN NaN NaN 0.043000 NaN 0.194357
SUB-SAHARAN AFRICA 0.230714 0.119 0.2455 NaN 0.228333 0.2640 0.311406
WESTERN EUROPE NaN NaN NaN 0.041 0.029389 0.1002 NaN

The pivot function works like the pivot_table function but does not do any aggregation. Therefore it will throw an error if you have duplicate index rows.

Try changing the values parameter to be a list of of columns maybe Agriculture, Service and Industry. How does that change your table?

6.5.1. Project

Add a “form of government” column to your data frame. There may be other alternatives for finding the data besides the web page I’ve given you to scrape. If you don’t want to do screen scraping there may be a different easier route.

Then create a pivot table using the region as the rows, form of government as the columns, and summarize the gdp in tabular form.

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