Trend Line

Trend lines are used to graphically display trends in data and forecast their future changes. This type of analysis is named regression analysis. By using regression analysis, the user can extend a trend line in a chart beyond the actual data to forecast future values.

See below an example of a trend line created with the forecast for three points forward:

To quickly set up data series format, use the Data Series side panel tab.

The following trend line settings are available:

Setting up trend line type.
Setting up trend line displaying in the legend.
Setting up trend line displaying in the chart plot area.
Setting up trend line values forecast.
Setting up peak interval.

For advanced setup of the trend line format, use the Trend Line Format dialog box.

Quick Setup of Trend Line

To set up a trend line, use the Trend Line group on the Data Series side panel tab.

Make sure that the side panel is displayed.
Select the chart in the working area.
Select the Format radio button on the side panel and go to the Data Series tab.

In the Type drop-down list select a line type:

Linear. This type is used with simple line data sets. A linear trend line can be applied for a value that is increasing or decreasing at a steady rate.
Logarithmic. A logarithmic trend line is used when the rate of change in the data increases or decreases quickly and then levels out. A logarithmic trend line can be used for both negative and positive data values.
Exponential. An exponential trend line is a curved line that should be used when data values rise or fall at constantly increasing rates. This trend line type cannot be used for the data that contains zero or negative values.
Power. A power trend line gives the best results when used with data sets that compare measurements that increase at a specific rate. An example of such a dependency is the acceleration of a race car at 1-second intervals. A power trend line cannot be used if the data contains zero or negative values.
Mean Value. Trend line goes through the mean value of data series. Such trend line enables the user to view dynamics of changing the considered value depending on the mean value.
Peak Values. The following trend lines are plotted: the line that goes through the maximum value of data series and the line that goes through the minimum value of data series.

A trend line is most accurate when its determination coefficient value (r2) is close to 1.

To show a trend line in the chart area in the desktop application, select the Line checkbox. A trend line icon will be added to the chart legend. After this trend line parameters can be set up (color, type and width of the trend line).

In the web application, trend lines are always displayed. To set up trend line parameters, use the Line parameters group.

A trend line in a chart can be controlled with the chart legend:

To hide a trend line, click the trend line icon in the legend with the main mouse button. The trend line will be hidden in the chart plot area and the legend icon is highlighted with gray.
To show a previously hidden trend line in the chart, click the trend line icon in the legend with the main mouse button. The trend line appears in the chart plot area.

To display trend line marker in the chart legend, select the Show in Legend checkbox.

After the checkbox is selected, additional marker parameters can be set up:

Redefine Name in Legend. When the checkbox is selected, the user can change name of the legend element that corresponds to the trend. By default, the name is created as follows: trend type (series type). For example: Linear trend (Bryansk region).

The Forward Forecast and Backward Forecast parameters are available for all trend types, except for the Mean Value and Peak Values types.

Using the value editor or manually set the number of steps in the trend line values forecast.

The Peak Interval parameter is available only for the Peak Values trend type.

Using the value editor or manually set the interval, at which to calculate peak series values.

To delete the selected trend line:

Deselect the Trend Line checkbox on the Data Series side panel tab.
Select Delete Trend Line in the trend's context menu.

NOTE. The command is available only in the desktop application.

After executing one of the operations the trend line is deleted from the chart.