pandas DataFrame.dot() Method Implementations
1. With Series Data
All the multiplied values are then added to get the dot product.
Python3
# Create a DataFramedf = pd.DataFrame({ 'A': [1, 2, 3], 'B': [4, 5, 6], 'C': [7, 8, 9]})# Create a Seriesseries = pd.Series([0.1, 0.2, 0.3], index=['A', 'B', 'C'])# Dot product with a Seriesresult_series = df.dot(series)print("Dot product with Series:")print(result_series) |
Output:
Dot product with Series:
0 3.0
1 3.6
2 4.2
dtype: float64
Explanation:
- Dot product for row 0: 1×0.1+4×0.2+7×0.3=3.01×0.1+4×0.2+7×0.3=3.0
- Dot product for row 1: 2×0.1+5×0.2+8×0.3=3.62×0.1+5×0.2+8×0.3=3.6
- Dot product for row 2: 3×0.1+6×0.2+9×0.3=4.23×0.1+6×0.2+9×0.3=4.2
2. With Dataframe
Python3
# Creating a DataFrame df1df1 = pd.DataFrame([[0, 1, -9, 1], [9, 1, 0, 1], [1, 3, 1, -1], [1, 1, 8, 1]])# Creating another DataFrame df2df2 = pd.DataFrame([[5, 3, 7, 4], [1, 3, 4, 3], [4, 3, 8, 6], [5, 8, 2, 8]])# Calculating dot productresult = df1.dot(df2)# Printing the resultprint(result) |
Output:
0 1 2 3
0 -30 -16 -66 -43
1 51 38 69 47
2 7 7 25 11
3 43 38 77 63
Explanation:
- Each row in the resulting DataFrame represents the dot product of the corresponding row in
df1and the columns indf2. - For example, the first row (row 0) is calculated as follows:
- 0×5+1×3+(−9)×7+1×4=−300×5+1×3+(−9)×7+1×4=−30
- 0×1+1×3+(−9)×3+1×8=−160×1+1×3+(−9)×3+1×8=−16
- 0×4+1×3+(−9)×8+1×2=−660×4+1×3+(−9)×8+1×2=−66
- 0×5+1×8+(−9)×2+1×8=−430×5+1×8+(−9)×2+1×8=−43
- The same logic is applied to calculate each element in the resulting DataFrame.
3. With Numpy Array
Python3
# Creating a DataFrame df1df1 = pd.DataFrame([[0, 1, -9, 1], [9, 1, 0, 1], [1, 3, 1, -1], [1, 1, 8, 1]])# Creating a NumPy arraynumpy_array = np.array([5, 3, 7, 4])# Calculating dot product with NumPy arrayresult = df1.dot(numpy_array)# Printing the resultprint(result) |
Output:
0 -56
1 52
2 17
3 68
dtype: int64
Explanation:
Each row represents the dot product of the corresponding row in the original DataFrame df1 with the NumPy array numpy_array.
- For the first row: 0 * 5 + 1 * 3 + (-9) * 7 + 1 * 4 = -56
- For the second row: 9 * 5 + 1 * 3 + 0 * 7 + 1 * 4 = 52
- For the third row: 1 * 5 + 3 * 3 + 1 * 7 + (-1) * 4 = 17
- For the fourth row: 1 * 5 + 1 * 3 + 8 * 7 + 1 * 4 = 68
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