Some instances where you may want to adjust the transparency would be if you had two line/scatter plots that intersected. To see the data for both plots, one should be made partially transparent.

  
Graph on left has full color, hiding the magenta line/scatter plot.
Graph on the right has transparent color, allowing the full graph to be viewed.

Another instance would be if there were an image background behind the graph. The graph fill could be adjusted so that the entire image was visible.

  
Graph on left has full color, hiding the background image.
Graph on the right has transparent color, allowing the full background image to be viewed.

In this article, we will adjust the opacity value of a line/scatter plot fill, add a second line/scatter plot, and adjust the opacity value of the second plot fill. Download the sample file NewsletterLine.DAT to follow along with the tutorial. Alternatively, apply the steps used to your own data set.

Creating a Line/Scatter Plot and Adding Transparency
Probably the most common place to use partial transparency would be in the plot's fill. This section details editing the plot's fill to include transparency.

1. Open Grapher 8.
2. Choose the Graph | 2D XY Graphs | Line/Scatter command.
3. The Open Worksheet dialog appears. Select the sample file NewsletterLine.dat and click the Open button. A line/scatter plot is drawn using the default properties.
   
   A line/scatter plot is created with the default properties.

4. In the Object Manager, select the Line/Scatter Plot 1 object. The plot properties are displayed in the Property Inspector.
5. In the Properties Inspector, click on the Fill tab to open the fill properties.
6. Next to the Pattern command, click the empty box. Select the Solid fill pattern. The plot is automatically filled with a solid black color.
7. To the right of the Foreground command, click the Black color to open the color palette. Select Green from the color palette and the line/scatter plot is updated with a green fill.
8. Next to Foreground Opacity, change the 100% to 40% by either highlighting the 100%, typing 40, and pressing the Enter key on the keyboard or by using the up and down arrows next to the 100% until the number shows 40% and pressing the Enter key on the keyboard. The line/scatter plot fill is updated with a 40% opacity fill.
   
   Add semi-transparent fill to any line/scatter plot.

Adding a Second Plot with Partially Transparent Fill
Adding a second line/scatter plot to the current graph is an easy way to compare identical X and Y variables over a different time range or a different location. For example, Line/Scatter Plot 1 could be displaying sales at store location A and Line/Scatter Plot 2 could be displaying sales at store location B. Alternatively, Line/Scatter Plot 1 could be displaying profit of store location A in 2008 and Line/Scatter Plot 2 could be displaying profit of store location A in 2009.

1. Select Graph 1 in the Object Manager.
2. Choose the Graph | Add to Graph | Plot command.
3. In the Select Plot Type dialog, select Line/Scatter Plot and click the OK button.
4. In the Choose Axes dialog, click the OK button, accepting the default values.
5. In the The Open Worksheet dialog, select the NewsletterLine.dat file and click the Open button. A Line/Scatter Plot 2 object is added to Graph 1 object using the default properties.
6. In the Object Manager, select the Line/Scatter Plot 2 object.
7. In the Property Inspector, click on the Plot tab to open the general plot properties. Change the Y column to Column E:. The plot automatically updates.
8. Click on the Fill tab to open the fill properties.
9. Next to the Pattern command, click the empty box. Select the Solid fill pattern. The plot is automatically filled with a solid black color.
10. To the right of the Foreground command, click the Black color to open the color palette. Select Cyan from the color palette and the line/scatter plot is updated with a cyan fill.
    
    When the cyan plot is 100% opaque, it hides a portion of the green plot.

11. Next to Foreground Opacity, change the 100% to 40% by either highlighting the 100%, typing 40, and pressing the Enter key on the keyboard or by using the up and down arrows next to the 100% until the number shows 40% and pressing the Enter key on the keyboard. The line/scatter plot fill is updated with a 40% opacity fill.
    
    When the cyan plot is 40% opaque, it does not hide the green plot.
    This creates a more informative graph, because all data can be viewed.

Adjusting Opacity for Text
The transparency feature can be used for other features of the graph, in addition to use described above. The following example shows using transparency for text. This is excellent for water marks or text boxes that need to be placed in front of objects that need to be fully visible. Both drawn text and text that is part of a graph, such as tick mark labels, axes labels, graph titles, and data labels, can utilize transparency. The opacity for text is controlled in the Text Editor. To draw text on the graph and adjust the opacity:

1. Choose the Draw | Text command. Click on the screen where you wan the text to appear.
2. In the Text Editor, type the text that should appear on the graph, such as Draft.
3. Highlight the text and change any properties of the text, such as the size or color.
4. Change the 100% value beneath the Opacity command to any value between 0 and 100, such as 20%.
   
   Adjust the opacity of text in the Text Editor.

5. Click the OK button to save changes. The text will appear on the graph.
6. If you want the text rotated, you can choose Arrange | Free Rotate and rotate the text to any desired position.
7. If you want the text behind all other drawn objects, like the graph, you can use the Arrange | Move to Back command.
8. You can also click on the text and move it on the screen to a new position.
   
   Text opacity is useful when drawing text on a graph.

Adjusting Opacity for Lines
Any line can have transparency added to it. This works for drawn lines or for lines that are part of the graph, such as line/scatter plot lines, axis lines, or grid lines. To draw a spline line on the graph and adjust the opacity:

1. Choose the Draw | Spline Polyline command.
2. Click on the screen to draw the polyline. When finished drawing the line, press the Enter key on the keyboard or double click on the last point in the line to end drawing mode. Press ESC on the keyboard to return to selection mode.
3. Click on the Spline Polyline 1 object in the Object Manager to select it.
4. In the Property Inspector, click on the Line tab to edit line properties.
5. Change the Opacity value to any desired value between 0% and 100%, such as 80%.
6. Make any other changes to the line, such as adding an arrow or adjusting the color or width.
   
   Line opacity is useful when drawing a polyline on a graph.
   The additional text "POI" is pointing out a point of interest on the graph.

Adjusting Opacity for Symbols
Any symbol can have transparency added to it, as well. This works for drawn symbols or for symbols that are a part of the graph, like the symbols on a line/scatter plot. This can be especially useful if the line behind the line/scatter plot has drastic changes near where a symbol is displayed. To add symbols to our existing graph and adjust the opacity of the symbols:

1. Click once on the Line/Scatter Plot 1 in the Object Manager.
2. In the Property Inspector, click on the Symbol tab to open the symbol properties.
3. Change the Symbol frequency to 5 to show every fifth symbol.
4. Change the Symbol to the desired shape by clicking on the existing symbol and selecting a new symbol in the drop down window.
5. Change the symbol Line color and the Fill color to the desired colors.
6. Change the and Fill opacity to be able to see through the symbols.
7. Make any other desired changes, such as to the symbol Size or rotation Symbol angle.
   
   Symbol opacity is useful to see the data line through the symbol on a graph.

Adjusting Opacity for Magnifiers
Magnifiers are areas of the graph that have been enlarged and included as a subset to the graph. The area that connects the original graph and the magnified area is called the connector. For more information on magnifiers, see the Issue 61 graph magnifiers article. In the below steps, we are adding a drawn inset zoom. This will allow the drawn items, like the arrow, to appear in the magnified area. To add an inset zoom and change the opacity of a connector area:

1. Choose Draw | Inset Zoom.
2. Hold down the left mouse button and drag a rectangle around the area you wish to enlarge.
3. When the rectangle is surrounding the entire area, release the left mouse button. The inset is automatically added to the page.
4. Click on the Inset Zoom 1 object in the Object Manager.
5. In the Property Inspector, click on the Connector tab to open the connector properties.
6. Open the Fill style section and change the Foreground color to another color, if desired.
7. Change the Foreground Opacity to any value between 0% and 100%, such as 25%.
   
   Inset zoom areas are useful to magnify both the graph and the drawn objects.