Exercise n. 2 - U.S.A. president's popularity

The file which follows contains data on the popularity of the U.S.A. president George W. Bush (source: http://www.presidency.ucsb.edu).
Produce a report which satisfies the requests which follow:

1) Find how many times the percentage of approving people was greater than the percentage of disapproving people under the same date.

2) Find dates which correspond to the maximum and to the minimum percentage of approving people.

3) Let's suppose that each percentage of approving people holds from its own date to the day before the percentage which follows. What is the average percentage of approving people during the whole presidency? (Notice that each percentage has to be weighted by the number of days of validity. If, for instance, the percentage is 75 for 30 days and 65 for 20 days, the average percentage is (75 * 30 + 65 * 20) / (30 + 20) = 71.)

4) Create a table with the maximum and the minimum percentage of approving and disapproving people for each month of each year of presidency.

5) Use the previous table to calculate the most favourable month of the presidency, i.e. find the month with the greatest average of maximum percentage of approving people.

6) Find dates which correspond to the maximum and to the minimum percentage of disapproving people for each year of presidency.