Calculate Area
The Graph Tools | Plot Tools | Calculate Area command computes the area under a line/scatter plot, ribbon/wall plot, or 3D XYZ line/scatter plot. When calculating area for 3D XYZ line/scatter plots, the area is calculated for the X, Y plane. The area is reported in the graph's X, Y units using zero as the base line.
To Calculate the Area:
- Create a line/scatter, ribbon/wall, or 3D XYZ line/scatter plot.
- Select the plot in the Object Manager or plot window.
- Click the Graph Tools | Plot Tools | Calculate Area command.
- Enter a baseline value into the Area Baseline Value dialog and click the OK button.
The baseline value is the Y value used to calculate the area. The area is calculated from the curve to the baseline value.
After the Calculate Area command is selected, a report window opens containing the area and information such as the data file, X variable, and Y variable used to create the plot. The area is reported in the graph's X, Y units.
Area Tip
The area is calculated by finding the area between the plot and baseline value entered in the Area Baseline Value dialog. If any part of the plot extends below the baseline value, a negative area is calculated and this value is added to the total area. The area report displays area Above Baseline Area, Below Baseline Are a, and Total Area.
The X values are selected based on the X values that are shown in the plot. All of the plot is used to calculate the area. If you want the area only under a certain range of X values, you need to limit the plot to only that range. The easiest way to do this is to set the Minimum and Maximum rows for the plot or to clip the plot to the axis limits.
Grapher does not interpolate between data points. Rather, the area is calculated between each adjacent set of XY points. Grapher sums these areas to display the final area value.