Trend lines
A trend line is a visual representation of the direction of values over a period of time. Trend lines show trends over time, by visualizing the direction of values and how fast the values change.
![](https://play.vidyard.com/fwWiMDpwQe8JAEj5sti18w.jpg)
Which visualizations have trend lines
Visualization | Trend lines |
---|---|
Bar chart | Yes |
Line chart | Yes |
When to use trend lines
A single trend line can be added to a chart to smooth out fluctuations in data, and to show any trends more clearly.
More than one trend line can be added to a chart, showing different types of trends or different values.
Types of trend lines
Average
An average trend line shows the average value of the data, for the time period being analyzed.
A bar chart showing sales per month. An average trend line is shown with a dashed red line.
![Click to view full size A bar chart showing sales per month. An average trend line is shown with a dashed red line.](../../Resources/Images/ui_gen_TrendLinesAverage_922x603.png)
Linear
A linear trend line shows increase or decrease of values at a steady rate. Linear trend lines are usually used with simple linear data sets.
A bar chart showing sales per month. An linear trend line is shown with a dashed red line.
![Click to view full size A bar chart showing sales per month. An linear trend line is shown with a dashed red line.](../../Resources/Images/ui_gen_TrendLinesLinear_929x602.png)
Polynomial (second, third, fourth degree)
A polynomial trend line is a curved line used on fluctuating data.
The number of data fluctuations can determine the order of the polynomial. A second degree polynomial trend line has one hill or valley, a third degree polynomial trend line has up to two hills or valleys, and a fourth degree polynomial has up to three hills or valleys.
A bar chart showing sales per month. Polynomial trend lines of second, third, and fourth degree are shown with dashed red, yellow, and green lines respectively.
![Click to view full size A bar chart showing sales per month. Polynomial trend lines of second, third, and fourth degree are shown with dashed red, yellow, and green lines respectively.](../../Resources/Images/ui_gen_TrendLinesPolynomialsAll_932x606.png)
Exponential
An exponential trend line is a curved line used when data values rise or fall at increasingly higher rates.
A bar chart showing sales per month. An exponential trend line is shown with a dashed red line.
![Click to view full size A bar chart showing sales per month. An exponential trend line is shown with a dashed red line.](../../Resources/Images/ui_gen_TrendLinesExponential_931x604.png)
Logarithmic
A logarithmic trend line is a curved line used when the rate of change in data increases or decreases quickly, before leveling out.
A bar chart showing sales per month. A logarithmic trend line is shown with a dashed red line.
![Click to view full size A bar chart showing sales per month. A logarithmic trend line is shown with a dashed red line.](../../Resources/Images/ui_gen_TrendLinesLogarithmic_929x604.png)
Power
A power trend line is a curved line used with data sets that compare measurements that increase at specific rates.
A bar chart showing sales per month. A power trend line is shown with a dotted red line.
![Click to view full size A bar chart showing sales per month. A power trend line is shown with a dotted red line.](../../Resources/Images/ui_gen_TrendLinesPower_935x608.png)