Since the ratio of sodium to potassium seems to predict when to use drug Y, you can derive a field that contains the value of this ratio for each record. This field might be useful later when you build a model to predict when to use each of the five drugs.

1. To simplify your flow layout, start by deleting all the nodes except the drug1n.csv Data Asset node.
2. Place a Derive node on the canvas and connect it to the drug1n.csv Data Asset node.

   

3. Double-click the Derive node to edit its properties.
4. Name the new field Na_to_K. Since you obtain the new field by dividing the sodium value by the potassium value, enter Na/K for the expression. You can also create an expression by clicking the calculator icon. This opens the Expression Builder, a way to interactively create expressions using built-in lists of functions, operands, and fields and their values.
5. You can check the distribution of your new field by attaching a Histogram node to the Derive node. In the Histogram node properties, specify Na_to_K as the field to be plotted and Drug as the color overlay field.

   

6. Right-click the Histogram node and select Run. A histogram chart is added to the Outputs pane. Based on the chart, you can conclude that when the Na_to_K value is around 15 or more, drug Y is the drug of choice.