Defining a Basic Lattice

Setting Grid Dimensions

Assume you want a grid of five plots. Before starting to write code, you must first decide what grid dimensions you want to set (how many columns and rows) and whether you want to permit an empty cell in the grid. If you do not want an empty cell, you must limit the grid to five cells, which gives you two choices for the grid dimensions: five columns by one row (5x1), or one column by five rows (1x5).

To specify grid size, you use the ROWS= and COLUMNS= options in the LAYOUT LATTICE statement. These options can be used in three ways to create the following grid, which contains one row and five columns:

layout lattice / columns=5 rows=1; /* plot definitions */ endlayout;	This makes the grid size explicit.
layout lattice / order=columnmajor rows=1; /* plot definitions */ endlayout;	To specify only one grid row, also specify ORDER=COLUMNMAJOR. In this case, there will be as many grid columns as there are plot definitions. This is the recommended way to create a row of plots.
layout lattice / columns=5; /* plot defintions */ endlayout;	When only the number of columns is specified, you place a limit on how many plots can appear in one row. If you were to include more than five plot definitions, additional rows (with five columns) would be added automatically because ORDER=ROWMAJOR by default.

If you are willing to have an empty cell in the grid, you could use a 2x3 or a 3x2 grid:

layout lattice / columns=3 rows=2 ;
endlayout;

Note: The LAYOUT LATTICE statement honors the full specification of columns and rows, unlike the LAYOUT GRIDDED statement, which honors only COLUMNS= or ROWS=, depending on the ORDER= setting.

By default, the layout uses the ORDER=ROWMAJOR setting to populate grid cells. This specification essentially means "fill in all cells in the top row (starting at the top left) and then continue to the next row below":

layout lattice / columns=3 rows=2 ;
  /* plot1 definition */
  /* plot2 definition */
  /* plot3 definition */
  /* plot4 definition */
  /* plot5 definition */
endlayout;

Alternatively, you can specify ORDER=COLUMNMAJOR, which means "fill in all cells in the left column and then continue to the next column to the right":

layout lattice / columns=3 rows=2 order=columnmajor ;
  /* plot1 definition */
  /* plot2 definition */
  /* plot3 definition */
  /* plot4 definition */
  /* plot5 definition */
endlayout;

Setting Gutters

To conserve space, the default LATTICE layout does not include a gap between cell boundaries. In some cases, this might cause the cell contents to appear too congested. You can add a vertical gap between all cells with the COLUMNGUTTER= option, and you can add a horizontal gap between all rows with the ROWGUTTER= option. If no units are specified, pixels (PX) are assumed.

layout lattice / columns=3 rows=2 columngutter=5 rowgutter=5 ;
  /* plot1 definition */
  /* plot2 definition */
  /* plot3 definition */
  /* plot4 definition */
  /* plot5 definition */
endlayout;

Note that by adding gutters, you do not increase the size of the graph. Instead, the cells shrink to accommodate the gutters. Depending on the number of cells in the grid and the size of the gutters, you will frequently want to adjust the size of the graph to obtain optimal results, especially if the cells contain complex graphs. For more information, see Adjusting the Graph Size.

Defining Cells

Several valid techniques are available for indicating the contents of a cell:

Technique	Example	Advantages	Disadvantages
stand-alone plot statement	scatterplot x= y=;	simplicity	can't adjust axes can't have overlays can't have cell headers
layout block	layout overlay; scatterplot x= y=; seriesplot x= y=; endlayout;	cell can contain a complex plot axes can be adjusted other layout types can be used	can't have cell headers
cell block	cell; layout overlay; scatterplot x= y=; seriesplot x= y=; endlayout; endcell;	makes it easy to see cell boundary in code required if a cell header is desired	adds to program length when no cell header is desired

The following code fragment for a LATTICE layout shows a simple example:

entrytitle "Simple 3x2 Lattice with Five Cells Populated";
layout lattice / columns=3 rows=2 columngutter=10 rowgutter=10;
  
  /* stand-alone plot statements define cells 1-3 */
  boxplot x=sex y=age;
  boxplot x=sex y=height;
  boxplot x=sex y=weight;

  /* overlay blocks define cells 4-5 */
  layout overlay;
    scatterplot y=weight x=height;
    pbsplineplot y=weight x=height;
    entry halign=right "Spline" / valign=bottom;
  endlayout;

  layout overlay; 
    scatterplot y=weight x=height;
    loessplot y=weight x=height;
    entry halign=right "Loess " / valign=bottom;
  endlayout;
	 
endlayout;

Simple 3x2 Lattice with Five Cells Populated

In the examples shown to this point, a LATTICE layout produces the same result as a GRIDDED layout. We can now look at features that are not available with the GRIDDED layout.

Adding Cell Headers

To add cell headers to the grid, you must specify a CELL block that contains a nested CELLHEADER block. The CELLHEADER block can contain one or more ENTRY statements, or it can contain other statements (DISCRETELEGEND, for example).

entrytitle "Simple 3x1 Lattice with Cell Headers";
layout lattice / columns=3 rows=1;
   
  /* cell blocks cells 1-3 */
     cell;
       cellheader;
         entry "Spline Fit";
       endcellheader;
       layout overlay;
         scatterplot y=weight x=height;
         pbsplineplot y=weight x=height;
       endlayout;
     endcell;

     cell;
       cellheader;
         entry "Loess Fit";
       endcellheader;
       layout overlay;
         scatterplot y=weight x=height;
         loessplot y=weight x=height;
       endlayout;
     endcell;

     cell;
       cellheader;
         entry "Regression Fit";
       endcellheader;
       layout overlay; 
         scatterplot y=weight x=height;
         regressionplot y=weight x=height;
       endlayout;
     endcell;
endlayout;

You can enhance any cell header in the following way:

nest a GRIDDED layout in the CELLHEADER block
set BORDER=TRUE on the LAYOUT GRIDDED statement
add the ENTRY statement(s) to the GRIDDED layout.

Because the GRIDDED layout fills the cell header space above the plot wall, its border aligns nicely with the plot.

You can further enhance the cell header by making the GRIDDED layout's background opaque and setting a background color for it. To ensure that the color remains coordinated with the current style, you could choose any of several style elements that define light background colors, such as GraphHeaderBackground, GraphBlock, or GraphAltBlock. Note that several style definitions set the GraphHeaderBackground color to be the same as the GraphBackground color. For styles like LISTING and JOURNAL, the background is white.

As a final enhancement, you could coordinate the text color for the cell headers with a visual attribute in the plot. For example, if you are displaying a fit plot in the cell, you could set the text color to match the color of the fit line. The TEXTATTRS= option in the ENTRY statement can be used to set the text properties. The default settings for TEXTATTRS= are derived from the GraphValueText style element. For more information on ENTRY statements, see Adding and Changing Text in a Graph.

The following code enhances the cell header block of the first cell. Similar code would be used to enhance the header blocks of the other two cells:

cellheader;
  layout gridded / border=true opaque=true
                   backgroundcolor=GraphAltBlock:color;
    entry "Spline Fit" / textattrs=(color=GraphFit:contrastColor);
  endlayout;
endcellheader;

Simple 3x1 Lattice with Enhanced Cell Headers

If you have a lengthy text description to add to a cell header, you should use multiple ENTRY statements to break the text into small segments; otherwise, the text might be truncated. Also, for a given row, if the number of lines of text in the cell headers varies, a uniform cell height is maintained across the row by setting all the row headers to the height needed by the largest cell header.