I am comfortable using Machine learning on my train data and test data and validate it.
But the question here is if I want to predict a single variable how do I do it?
Let's suppose I have done feature selection using lasso or applied PCA or done feature engineering like transformation or scaling but when I want to utilize it for new data, maybe single data I am getting confused. Should I have to follow all the steps mentioned above even for the single row of data or how do I proceed with this. Please suggest.