data visualization: basics

A line chart, also referred to as a fever chart, is an effective way to show trends with specific types of data.

• It compares changes in a single value, like a rate or index.
• Values should be consecutive. (daily, monthly. yearly, etc.)
• It should compare at least three changes in the value. (If you only have two changes, use percent change.)
• It should illustrate a trend.
• It can include multiple lines to compare multiple values.

Upload your data

From any spreadsheet, click on the word "docs" to return to the main Google Docs page and click the "Upload" button.

On the Upload page, click "Select files to upload" and navigate to "LineChart-CrimeRates.xls" and select it. At the bottom of the Upload page, click the "Start upload" button.

Once the upload is done, click the file link to open the spreadsheet.

Select your Gadget: Go to the Insert menu and select Gadget. In the pop-up box, click the "Charts" link and scroll down until you find the interactive line chart. Then click "Add to spreadsheet."

Change the Range field to read "Sheet1!A1:B8"

Change Legend to "On Top."

Change the "Axis minimal value" to zero and the "Axis maximum value" to 30. Then click "Apply and close."

Tip: As we discussed earlier, a baseline is the bottom of a chart and where the chart is drawn from. A bar chart usually uses a baseline of zero, but a line chart can use whichever baseline best illustrates a trend. This does distort data somewhat so clear labeling is critical. Let's look at some examples.

Your chart should look like the one below on the left. With a zero baseline, the data is flat and some nuance is missing. Click "Edit" and change "Axis minimal value" to 25. Then click "Apply." The result will be similar to the chart in the middle. While this does distort the data, it is much easier to see the trend. So when is this bad? If you were to change the dimensions of the chart as done in the one on the right, the data shows radical swings up and down. We know that is not the case, so avoid doing this.

If you want to compare the crime rates to each other, extend the range. Click "Edit" and change B8 to D8. You should change the "Axis minimal value" to 0 in this case and delete the "Axis maximum value" so the gadget can figure out how to redraw the chart. Then click "Apply and close." The result will be similar to the chart on the right. This can be an effective way to compare multiple rates/trends.

Get your embed code: Click the the triangle on the top right of the gadget. In the menu, select "Publish Gadget." Copy and paste the code into a page on your site.