The two drop down lists below the chart let´s you compare two data series from separate tables.

It is easier to follow the tutorial steps if you download the excel *.xlsx file:
Compare data series in a chart.xlsx

### Drop down lists

1. Select cell B21
2. Go to tab "Data"
3. Click "Data Validation" button
4. Allow: Select List

Repeat above steps with cell D21 and use this Data Validation formula:

The following post explains how to use table names in drop down lists and conditional formatting formulas: How to use a table name in data validation lists and conditional formatting formulas

### Named ranges

There are two tables in sheet Calculation. Let´s create named ranges and later we are going to use them as series values in a chart.

1. Go to sheet Calculation
2. Go to tab "Formulas"
3. Click "Name Manager" button
4. Click "New..." button
5. Name: Chrt_tbl1
6. Refers to: =INDEX(Table1,0,MATCH(Chart!\$B\$21,Table1[#Headers],0))
7. Click OK

Create another named range, named Chrt_tbl2 and use this formula: =INDEX(Table1, 0, MATCH(Chart!\$D\$21, Table1[#Headers], 0))

Named ranges are really useful, this post demonstrates how to add values automatically to a chart: How to create a dynamic chart

### Insert chart

1. Go back to sheet "Chart"
2. Go to tab "Insert"
3. Click "Column" chart button | "Clustered column" chart button
4. Right click on the empty chart
5. Click "Add" button
6. Series name: Chart!\$B\$21
7. Series values: =Calculation!Chrt_tbl1 (Don´t forget to use the sheet reference!)
8. Click OK
9. Click "Add" button again
10. Series name: Chart!\$D\$21
11. Series values: =Calculation!Chrt_tbl2  (Don´t forget to use the sheet reference!)
12. Click OK
13. Click OK

The following post shows you how to select a series using both an index column and an index row: Dynamic chart – Display values from a table row or column