Sometimes, your chart data values are not so much different from each other. This results in a chart which doesn't help your audience to see any difference between series representing those values. Our sample data, shown in Figure 1 below explores how people of different age brackets choose their favorite colors. If you look closely at the data, you will realize that all values span between 285 and 365. So, does it makes sense to even discuss any value lower than 250 or above 370 for this data set. The answer to that question is not very easy to answer. Although we do show you how to show a more pronounced change in this tutorial, make sure you read The Ethics of Distortion box towards the end of this page.
Figure 1: What's your favorite color?
View and Edit Data
To quickly see the data for any chart, right-click (or Ctrl+click) the chart, and choose the Edit Data option.
When you create sample column and bar charts from this data using PowerPoint's defaults, you'll end up with charts akin to what you see in Figure 2, below. The chart on the top shows columns that are very similar in their heights. There really is no contrast highlighting the findings of our data. It's the same story with the bar chart below where the bars look almost similar in length.
Figure 2: A column chart and a bar chart with columns and bars that are very similar
The reason for lower contrast between values in these charts is that the Minimum and the Maximum values set for the Value Axis are calculated from a minimum value of zero. This actually makes the differences in the column height or bar widths so much less pronounced, and thus makes the chart much less effective as a visual medium.
The Value Axis
The value axis is the vertical axis on the left of a typical column chart, or the horizontal axis at the bottom for a bar chart (see Figure 2). Learn more about the chart axes.
Fortunately, you can easily choose your own maximum and minimum values. In the following steps, we are using our column chart as an example. However, the same techniques will work for bar charts too.
Follow these steps to change the minimum and maximum values on a chart axis in PowerPoint 2010 for Windows:
- First of all, take a look at your chart data and note what your maximum and minimum values are—our chart data that you saw in Figure 1 earlier on this page has a minimum value of 285, and a maximum value of 365. Now decide the maximum and minimum values to be assigned for your vertical axis. Considering our sample chart data, we decided to set our Minimum value to be 250 (less than 285) and the Maximum value to be 370 (more than 365).
- Now, select the value axis of the chart. Carefully right-click to access the contextual menu as shown in Figure 3, below. Within this contextual menu, chose the Format Axis option (refer to Figure 3 again). If you do not get the Format Axis option in the contextual menu, you may have right-clicked on another chart element. Make sure you then deselect anything in the chart, and then right-click on the value axis.
Figure 3: Format Axis option selected for the value axis
- Doing so opens the Format Axis dialog box, as shown in Figure 4, below.
Figure 4: Format Axis dialog box
- Within the Format Axis dialog box, locate the Minimum and Maximum options, highlighted in red within Figure 4, above. As you can see, the Minimum and Maximum options are set to Auto by default, which is indicated by the Auto radio buttons selected in front of these options.
- Select the Fixed radio button in front of the Minimum option, and then type a new value within the box, as shown highlighted in red within Figure 5, below. For our chart example, the Minimum value was changed to 250.
Figure 5: Minimum Vertical axis value changed
- Similarly, select the Fixed radio button in front of the Maximum option, and then type the Maximum value, as shown highlighted in red within Figure 6, below. For our chart example, the Maximum value was changed to 370.
Figure 6: Maximum Vertical axis value changed
- Once you are done, click the Close button within the Format Axis dialog box to get back to your slide. Now you can see that the maximum and minimum values on the value axis are changed to new values. If you compare the charts in Figure 7 with the charts in Figure 2, you will find that these changed charts provide a more pronounced contrast for the data.
Figure 7: Charts with changed Maximum and Minimum values on Vertical axis
- Save your presentation often.
The Ethics of Distortion
Yes, we did show you how you can change the maximum and minimum values on the value axis. This makes the difference between the various columns more pronounced. But chart purists differ, and in many ways they are right because although your comparisons are pronounced, they are also not the truth—at least not the whole truth. Many people in your audience may not see that your values do not begin from zero, and some charts created this way may forego the values within the axis altogether. So what should you do? The answer is to strike a balance. If you do alter the values to no longer start at zero, make that very apparent to your audience.
Make sure you add a note to that effect on your slide, and even draw the attention of your audience to this fact.
10 08 03 - Chart Axes: Set Minimum and Maximum Values on Value Axis (Glossary Page)