How can I improve the accuracy of my linear regression model ?
I have created a model to fit my data. when I extracted the results using sample_ppc and plotted it against my actual posterior, it looks fine. But, when I tried the same model with new data, it had a lot of deviation.
Initial Data
New Data
Green line is the actual data and red colored one is the predicted data.
It would be helpful if someone helps me out to increase the accuracy of my model