There are two methods in Grapher to add a line of constant value to your graph. The first is to add a function plot. The second is to add a grid line to an existing axis. Both methods are outlined below.

Function Plot:

To add a line of constant value using a function plot, you can use these steps:

- Click anywhere on the existing graph to select it.
- Click the
**Graphs | Add to Graph | Plot**command (). - In the
**Select Plot Type**dialog, select*Function Plot*and click*OK*. - In the
**Choose Axes**dialog, select the axes to use for the new constant value line and click*OK*. The plot is added using the default options. - Click on the
*Function Plot*in the**Object Manager**to select it. - In the
**Property Manager**, click on the**Plot**tab. - For a horizontal line, highlight the
*cos(X)*text next to*Y = F(X) =*and type the desired value for the horizontal line. For instance, you might type 30, if you want the line displayed at Y=30. - For a vertical line,
- Change the
*Type*from*Y=F(X)*to*X=F(Y)*. - Highlight the
*cos(Y)*next to the*X = F(Y) =*and type the desired value for the vertical line. For instance, you might type 400, if you want the line displayed at X=400.

- Change the
- Highlight the value 12 next to
*Last value*and type the axis maximum value. For a horizontal line, this should be the X maximum value. For a vertical line, this should be the Y maximum value. - Highlight the zero next to
*First value*and type the axis minimum value. For a horizontal line, this should be the X minimum value. For a vertical line, this should be the Y minimum value.

The line now extends the full length of the plot at the specified value. The line style and color can be changed on the **Line** tab in the **Property Manager**.

Axis Grid Lines:

Axis grid lines may be easier to use if you have many horizontal or vertical lines that you want to display. It may also be easier if the axis limits will change. To draw lines of constant value using the axis grid lines:

- Click on the existing worksheet or create a new worksheet.
- In one column, type each Y value for each horizontal line.
- In another column, type each X value for each vertical line.
- Save the data file.
- Click back on the plot window.
- For a horizontal line, click on the
*Y Axis*to select it. For a vertical line, click on the*X Axis*to select it. - In the
**Property Manager**, click on the**Grid Lines**tab. - Click the + next to the
*Worksheet Lines*section. - Check the box next to the
*Worksheet grid lines*option. - Change the
*None*option next to*Worksheet*to the worksheet file that was saved in step 4. - Change the
*Column*to the desired column. For horizontal lines, this is the column created in step 2. For vertical lines, this is the column created in step 3.

The line now extends the full length of the parallel axis. The line style and color can be changed in the *Worksheet line properties* section.

*Updated October 3, 2016*

## 0 Comments