NLP techniques to label unlabeled data in a dataset So I have a .xls file with negative and neutral reviews of a medicine. However, this dataset does not have labels. I converted this .xls into a dataframe and I am using the Spacy Lib. 

I have to use NLP techniques to label the data. Can you guys help me out on how to use NLP techniques to label this dataset as a neutral review or a negative review. So far, I did data cleansing (remove stop words, punctuation, etc.)

What are the next steps?
This is still a problem undergoing active research. I think it's commonly referred to as unsupervised labeling. If the dataset is not too large, it's probably more accurate and time efficient to either do it by hand, or hire someone on Mechanical Turk to do it.

If you're dead set on doing it automatically, trying some form of semi-supervised learning where you train it on a few examples, and then attempt to generalize is probably your best bet.