Defining a Basic Grid

Although you can generate a nice looking graph in a default GRIDDED layout, in most cases you will want more control over the grid, how it is populated, and the complexity of the cell contents.

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 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 the grid size, you use the COLUMNS= or ROWS= option in the LAYOUT GRIDDED statement. To use ROWS=, you must also specify ORDER=COLUMNMAJOR.

Two explicit specifications could be used to create the following grid, which contains one row and five columns:

layout gridded / columns=5;
  /* plot defintions */
endlayout;

When the number of columns is specified, you place a limit on how many columns can be displayed across a row. The COLUMNS= option is honored only if ORDER=ROWMAJOR (the default).

In the example code to the left, if you were to include more than five plot definitions, additional rows (with five columns) would be added automatically to accommodate all of the cells that are needed to display all specified plot definitions.

layout gridded / order=columnmajor
                              rows=1;
  /* plot definitions */
endlayout;

When the number of rows is specified, you place a limit on how many rows can be displayed down a column. The ROWS= option is honored only if ORDER=COLUMNMAJOR.

In the example code to the left, if you were to include more than five plot definitions, additional columns would be added automatically, but the grid would not wrap to a second row because the ROWS= setting limits the grid to a single row.

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

layout gridded / columns=3 ;
endlayout;

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." COLUMNS=1 by default when ORDER=ROWMAJOR, so you must specify an alternative setting to increase the number of columns in the grid:

layout gridded / columns=3 ;
  /* 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." ROWS=1 by default when ORDER=COLUMNMAJOR, so you must specify an alternative setting to increase the number of rows in the grid:

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

Setting Gutters

To conserve space, the default GRIDDED 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 gridded / columns=3 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 Sizing Issues

Defining Cells

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

Technique	Example	Advantages	Disadvantages
stand-alone plot statement or text statement	scatterplot x= y=;	simplicity	can't have overlays can't adjust axes, borders, or backgrounds (these are layout options)
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	more complexity

The following definition for a GRIDDED layout shows a simple example:

entrytitle "Simple 3x2 Lattice with Five Cells Populated";

layout gridded / columns=3;
  
  /* 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

Notice that some Y-axis labels are too close to their neighboring plots. You can use the COLUMNGUTTER= and ROWGUTTER= options to add gutters between all columns and rows. The following layout statement defines a grid with 30-pixel gutters:

layout gridded / columns=3 columngutter=30 rowgutter=30 ;

Notice that adding gutters visually separates graphs, but it does not increase the overall graph size. To compensate for the gutters, the cells become smaller. This same behavior is observed by other multi-cell layouts, as well.