Now let's take a look at what factors might influence Drug, the target variable. As a researcher, you know that the concentrations of sodium and potassium in the blood are important factors. Since these are both numeric values, you can create a scatterplot of sodium versus potassium, using the drug categories as a color overlay.

1. Place a Plot node on the canvas and connect it to the drug1n.csv Data Asset node. Then double-click the Plot node to edit its properties.
2. Select Na as the X field, K as the Y field, and Drug as the Color (overlay) field. Click Save, then right-click the Plot node and select Run. A plot chart is added to the Outputs pane.

   The plot clearly shows a threshold above which the correct drug is always drug Y and below which the correct drug is never drug Y. This threshold is a ratio -- the ratio of sodium (Na) to potassium (K).