Interpolation Lines

An interpolation line connects data values. Interpolation lines apply to line charts, area charts, scatterplots (except for 3-D scatterplots), difference area charts, mean variable in error bar charts, and close variable in high-low-close charts. (Interpolation does not apply to histograms.)

Note that a line in a line, area, or difference area chart is an interpolation line.

How to Add an Interpolation Line

  1. If you want to add an interpolation line that connects graphic elements in a particular group, select the group. If no graphic elements are selected, the Chart Editor will create an interpolation line through all graphic elements.
  2. From the menus choose:

    Elements > Interpolation Line

  3. Use the Interpolation Line tab to specify the interpolation method and to specify if interpolation continues through missing values.
  4. If necessary, use the Line Options tab to display a projection line.
  5. If necessary, use the Lines tab to specify the formatting for the interpolation line.
  6. Click Apply.

How to Edit an Interpolation Line

  1. Select the interpolation line.
  2. From the menus choose:

    Edit > Properties

  3. Use the Interpolation Line tab to specify the interpolation method and to specify if interpolation continues through missing values.
  4. If necessary, use the Line Options tab to display a projection line.
  5. If necessary, use the Lines tab to specify the formatting for the interpolation line.
  6. Click Apply.

How to Delete an Interpolation Line

  1. Select an interpolation line.
  2. Press Delete.

Using the Interpolation Line Tab

Straight. Connect the data values in succession by straight lines. This method is the same as the one used when a line chart is created.

Step. Draw a horizontal line through each data value, and connect the horizontal lines with vertical lines. Select Left Step, Center Step, or Right Step to indicate the data value's position on the horizontal line.

Jump. Draw a horizontal line through each data value. Select Left Jump, Center Jump, or Right Jump to indicate the data value's position on the horizontal line. Step and Jump work the same way except that Jump does not have vertical connecting lines.

Spline. Connect the data values by a cubic spline.

Interpolate line through missing values. By default, the Chart Editor breaks the line at missing values. You can select the check box to force the Chart Editor to continue the line through missing values.