Ajax data projectHow old are the playgrounds in Ajax? Sorting the Town’s file with if and else
The Town of Ajax publishes its playgrounds as open data, a point file of play sites with an INSTALL year for each one. Pickering’s open data hub, when we searched it on 22 October 2026, listed mostly Durham Region and conservation layers and no City of Pickering parks or playground file, so this project uses Ajax only. All figures in this section are counts we made ourselves from the Ajax download of that date.
Ajax playgrounds by age in 2026, our calculation (2026 minus the INSTALL year) from the Town of Ajax Playgrounds file; 73 rows have TYPE Playground| Age band in 2026 | Playgrounds | What the code asks |
|---|
| Under 10 years (installed 2017 or later) | 9 | age < 10 |
| 10 to 19 years | 33 | otherwise, age < 20 |
| 20 years or more (installed 2006 or earlier) | 31 | everything left over |
The file has 81 rows: 73 playgrounds, 3 skate parks, 3 splash pads and 2 sets of exercise equipment. Install years run from 1999 to 2020, and 42 of the 73 playgrounds went in during the 2000s. The youngest is 6 years old in 2026 and the oldest 27. Written as Python, the Grade 5 decision tree looks like this, and children of 10 or 11 type it line by line in our class:import csv
bands = {"under 10 years": 0, "10 to 19 years": 0, "20 years or more": 0}
ages = []
with open("ajax-playgrounds.csv", encoding="utf-8-sig") as f:
for row in csv.DictReader(f):
if row["TYPE"] != "Playground":
continue
age = 2026 - int(row["INSTALL"])
ages.append(age)
if age < 10:
bands["under 10 years"] += 1
elif age < 20:
bands["10 to 19 years"] += 1
else:
bands["20 years or more"] += 1
print(bands)
print("youngest", min(ages), "oldest", max(ages))
print("mean", round(sum(ages) / len(ages), 1))
ages.sort()
print("median", ages[len(ages) // 2])
Skip what does not fit
The first if checks the TYPE column and uses continue to jump past skate parks, splash pads and exercise equipment. Only the 73 playgrounds reach the age questions.
Ask in the right order
Is the age under 10? If not, is it under 20? If neither, it must be 20 or more. Swap the first two questions and every playground under 10 also passes the under-20 test first, so the counts go wrong.
Mean and median
Our run printed a mean of 17.6 years and a median of 18. The two are close here, and children work out why: most install years cluster in one decade, with no extreme values pulling the mean.
A date that is not what it seems
Age here means years since the INSTALL date in the file. It is not the age of every swing or slide: parts can be replaced without the file changing. Most rows were last edited in 2013 or 2014, and the Town’s record of the dataset was modified on 9 May 2021. A good data scientist asks how old the data is before trusting what it says about age.
Some columns are never printed in our classes. Location names can name schools or people, and one column records a staff account, so we leave them out and teach why. The NAME column is safer and interesting: among the playgrounds it says Main 54 times, Senior 18 times and Junior once, which a class can turn into a pie chart. The most common install year is 2006, with 9 playgrounds. Data used under the Town of Ajax - Open Data Licence v.1.0, which allows commercial use. Contains public sector Information made available under The Corporation of the Town of Ajax’s Open Data Licence. The Town does not endorse this page.
