I have trained a model for predicting the sale of items daily, such as daily car sales, with a machine learning model in Python. Now I get the new time real data (time series data). I want to retrain my mode. There are some issues:

  1. How much data I should use for retraining model, namely what's the time range of data or when I should retrain my model. For example use the new one day or one week et al., data to retrain model.

  2. What's condition of new data if I want to use the new data for retraining model.

  3. How to evaluate the stability of new training model, and How to know abnormal prediction for new model.


1 Answer 1


Once you trained your model, you have a measure of accuracy.

You should retrain your model when the accuracy drops below a certain threshold.

Another approach is to use a Bayesian model, in which you update your model with each new observation.

I would suggest looking into pymc3's examples

  • $\begingroup$ thanks for your valuable comments. I will check the documents you mentioned. Could you tell me how to know abnormal prediction if I used the new retrained model. $\endgroup$
    – tktktk0711
    Commented Aug 16, 2017 at 1:32

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