The message already gives a good hint for your question. Simple run the cells that create (import) those variables (or functions).
Every time you open the notebook, you must re-run all of the cells starting from the top.
@Alaasultan84 please make sure that you have imported the dataset correctly.
there are two probable reasons for this error
- You didn’t Import the dataset and tried to load the dataset.
- You didn’t execute the previous cells