5. Line Charts for Large Datasets

Overview

The line chart is the best way of displaying large datasets on a PowerPoint slide. Here I show you how to plot daily oil prices over a 3 year period.

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Summary

  1. Lesson Goal (00:04)

    The goal of this lesson is to learn how to create a line chart in PowerPoint.

  2. Creating the Line Chart (00:09)

    The line chart is useful when we have a large number of data points, and are especially useful if we want to track a variable over time. Line charts are often used to track the price of stocks or commodities like oil over time.

    We create a line chart by selecting the Insert tab, then Chart, then selecting a line chart. In the Excel window, each column of the table represents a line on the line chart. In our example, we create a chart with a single line, which tracks the oil price over time.

    Note that we generally don’t add data labels to a line chart, as the number of points would make the labels difficult to read. Instead, our formatting tends to focus on the axes of the chart.

  3. Formatting the Axes (01:40)

    The y-axis of the chart measures the value of each point on the line. By default, this starts at zero, however this may lead to the line occupying only a small portion of the chart area. We can change this by adjusting the minimum value of the axis. To do this, we right click the axis, and select Format Axis. In this pane, we can then adjust the minimum and maximum values for the axis under the Axis Options heading. If we set the minimum value just below the value of the smallest point, we can ensure that the line will occupy most of the chart area.

    The x-axis on a line chart usually shows time. By default, the chart will try to show a label for each point. If your chart shows daily data, the labels may be written vertically to try and fit in as many labels as possible. This can make the labels difficult to read. We can change this by adjusting the format and frequency of the labels.

    In order to make these changes, we right click the x-axis and select Format Axis. In this pane, the Number option allows us to adjust the Format Code used for the dates shown on our x-axis labels. In our case, we switch from a label showing day, month, and year to a label showing month and year only. As a result, we only have one label for each month instead of each day. Within the Format Axis pane, we can adjust the frequency of these labels. In the Axis Options section, the Major unit defines how often a label appears on our chart. In our example, we set this to 3 months, so that the number of labels is manageable. In addition to these changes, we may also need to adjust the font size of the labels to ensure that they fit the available space.

  4. Completing the Chart (04:19)

    After formatting the axes, we can make the usual formatting changes to complete our chart, including adding titles and adjusting font sizes.

    It’s also worth being aware of other types of line chart, including a stacked line chart and a 100% stacked line chart. These chart types are rarely used, as they can be difficult for audiences to understand intuitively. An area chart is likely to be preferable to either of these chart types.

Transcript

When we need to plot large amounts of data, bar charts can become difficult to read. When I have a data set of, say, over 15 data points, I'll normally use a line chart to plot this information. The perfect case for using line charts is when you're plotting a company's share price, or a commodity price, over time. Here you may have hundreds of data points, and a line chart is one of your best options. Let's say, for example, I'd like to chart the price of oil over the last 3 years. I'll start by inserting a chart, so I'll go to Insert, Chart, and select the line chart.

Then press OK to generate the line chart on our screen.

As you can see, Excel creates 3 lines, each with 4 data points, just to get us started. This chart will have only 1 line, so I'll move the blue region to only include Series 1.

The X axis dates will replace the 4 categories, and then the oil price information will be under the Series 1 column. Off-camera, I'll now paste in the data from my oil price.

Now when I minimize the Excel sheet, you can see our oil price appear as a line chart on our PowerPoint slide. Unlike with bar charts, we won't be adding data labels to our line chart, because there's simply too many data points to make these labels readable. Instead, we'll keep the Y axis in place, and read the oil price from the horizontal grid lines. Again unlike with bar charts, the axis on the line charts requires some formatting to make the chart more readable. Let's start with the Y axis.

So that the values consume most of the chart area, I'd like the Y axis to start at just below the lowest oil price value, which is around 75. To do this, I'll select the Y axis, right click, and select Format Axis.

I'll then go to the minimum axis options, and write in 70, which is my desired value.

When I close this dialog box, you can see that our values now take up our full chart area, which is exactly what we want. Now let's take a look at the X axis. I'll start by changing the chart area by making it wider, and I'll remove the legend because we have only one line in this chart, so a legend isn't needed. The first change I'd like to make to the X axis is to change the format of the labels. Currently, we're showing the day, the month, and the year. I'd like to just show the month and the year, so I'll select the X axis, right click, and format axis.

I'll select the number option, which allows us to change the date format, and then the format code. I'll write 3 M's, space, YY.

This format will show Jan 12, for the 3rd of January 2012, which is a much neater date format. I'll click Add, and then Close.

And as you can see, our labels have changed, but unfortunately they're overlapping. Let's make this more readable by changing the size of the label font. So I'll go to Home, and I'll select 14.

This is certainly an improvement, but I'd still like the month and year to appear on the same line. To do this, instead of showing every second month on the X axis, I'll show every third month. So again I'll go to the X axis, I'm going to select it, I'll right click, and format axis.

I'll then go to Major unit, change it manually, and enter 3 instead of 2.

I'll then close.

And you can see that our X axis labels now show every third month instead of every second month. And it's much easier to read. The last change I'll make will be to select the chart, and move the chart area slightly in from the right, so that the January 14 label can be easily read. Off-camera, I'll make some small editing changes, giving this slide a title, giving the chart a title, and cleaning up some of our font sizes to make them consistent. As this example has probably shown you, the line chart does require a lot more formatting than the bar chart. I'd encourage you to experiment with the various axis options available for the line chart, so you understand all of the ways in which these charts can be formatted. In this example, I used this simple line chart to show our oil price fluctuation. There are other line chart options available as well. If I go back to the Insert Chart options, you can see that we have the stacked line chart, and the one hundred percent stacked line chart. These are similar to the stacked column charts we've used in previous lessons. If you want to use a stacked chart for large data sets, I don't recommend using this option, because I think the audience doesn't intuitively grasp a stacked line chart. Instead, I'd advocate using an area chart, which I'll show you in the next lesson.

PowerPoint Essentials
Construct Charts for Your Data

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