1 files changed, 45 insertions, 0 deletions
diff --git a/calculate_precision.py b/calculate_precision.py
new file mode 100644
index 0000000..acf1391
--- /dev/null
+++ b/calculate_precision.py
@@ -0,0 +1,45 @@
+import csv
+
+DATA_FILE = "data.csv"
+THETAS_FILE = "thetas.csv"
+
+
+def load_thetas():
+    with open(THETAS_FILE) as f:
+        lines = f.readlines()
+        return float(lines[0]), float(lines[1])
+
+
+def load_data():
+    km = []
+    price = []
+    with open(DATA_FILE) as f:
+        reader = csv.reader(f)
+        next(reader)
+        for row in reader:
+            km.append(float(row[0]))
+            price.append(float(row[1]))
+    return km, price
+
+
+def mean(vals):
+    return sum(vals) / len(vals)
+
+
+def estimate_price(mileage, theta0, theta1):
+    return theta0 + theta1 * mileage
+
+
+def main():
+    kms, prices = load_data()
+    theta0, theta1 = load_thetas()
+    predicted_prices = [estimate_price(x, theta0, theta1) for x in kms]
+    mean_price = mean(prices)
+    r2 = 1 - sum((p - pp) ** 2 for p, pp in zip(prices, predicted_prices)) / sum(
+        (p - mean_price) ** 2 for p in prices
+    )
+    print(f"R-squared = {r2}")
+
+
+if __name__ == "__main__":
+    main()