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Unexpected results when using np.log1p on large arrays with negative values in NumPy 1.23

👀 Views: 0 đŸ’Ŧ Answers: 1 📅 Created: 2025-06-14
numpy logarithm data-preprocessing Python

I'm sure I'm missing something obvious here, but I'm relatively new to this, so bear with me. I'm working with unexpected results when using `np.log1p` on a large array that contains negative values. I thought `np.log1p(x)` computes the natural logarithm of one plus the input array, but when I apply it to an array that contains negative values, I get NaNs instead of the expected results. Here's a simplified version of my code: ```python import numpy as np data = np.array([-1.0, 0.0, 1.0, 2.0, 3.0]) result = np.log1p(data) print(result) ``` When I run this, I see the output: ``` [nan, 0.0, 0.69314718, 1.09861229, 1.38629436] ``` I was under the impression that `np.log1p` should handle the calculation for `0.0` correctly and return `0.0`, which it does, but I'm puzzled by the `NaN` for `-1.0`. I understand that the logarithm of zero or negative numbers is undefined, but I was hoping for some form of clarification or warning instead of simply getting `NaN`. Is there a way to preprocess the data to avoid this scenario or is there a better function that could handle such cases more gracefully? I've also tried using `np.clip` to limit the values, but that feels like a workaround rather than a solution. Any insights on how to handle negative values in this context would be much appreciated! I'm working on a API that needs to handle this. My development environment is Linux. Has anyone else encountered this? For context: I'm using Python on Windows 10. Is there a simpler solution I'm overlooking?