1. Data type mismatch: In VBA programming, data of numerical type must match the mathematical function used. If the data types do not match, the results may be biased. For example, when using the SIN function, you can only use radians, not degrees.
2. Rounding error: When floating-point numbers are used for calculation, rounding error may be caused. When the same piece of code is executed repeatedly, these rounding errors will accumulate, leading to the deviation of the results.
3. Numerical precision: The numerical precision of some mathematical functions may not be high enough, resulting in deviation of the results. This may affect some complex functions, such as trigonometric function, exponential function and logarithmic function.
4. Amount of data: If the amount of data processed is too large, it may lead to memory overflow or performance bottleneck, resulting in calculation deviation.
5. Code logic: If there are errors or defects in the code logic of the self-made function, it may also lead to deviations in the results. Therefore, when writing self-made functions, we should ensure the correctness of code logic.
To sum up, the way to deal with the deviation of self-compiled function results is to ensure the correctness of data type, rounding error and numerical precision, and to check the correctness of code logic. If the above methods can't eliminate the deviation, we should consider reconstructing the function to improve the performance and accuracy.