About crosstabs

Cross tabulation is a useful technique for analyzing data. By presenting data in a spreadsheet-like grid, a crosstab lets you view summary data instead of a long series of rows and columns. For example, in a sales report you might want to summarize the quarterly unit sales of each product.

In InfoMaker, you create crosstabs by using the Crosstab presentation style. When data is retrieved into the report, the crosstab processes all the data and presents the summary information you have defined for it.

An example

Crosstabs are easiest to understand through an example. Consider the Printer table in the EAS Demo DB. It records quarterly unit sales of printers made by sales representatives in one year. (This is the same data used to illustrate graphs in Chapter 13, “Working with Graphs.”)

**Table 14-1: The Printer table in the EAS Demo DB**
Rep	Quarter	Product	Units
Simpson	Q1	Stellar	12
Jones	Q1	Stellar	18
Perez	Q1	Stellar	15
Simpson	Q1	Cosmic	33
Jones	Q1	Cosmic	5
Perez	Q1	Cosmic	26
Simpson	Q1	Galactic	6
Jones	Q1	Galactic	2
Perez	Q1	Galactic	1
.	.	.	.
.	.	.	.
.	.	.	.
Simpson	Q4	Stellar	30
Jones	Q4	Stellar	24
Perez	Q4	Stellar	36
Simpson	Q4	Cosmic	60
Jones	Q4	Cosmic	52
Perez	Q4	Cosmic	48
Simpson	Q4	Galactic	3
Jones	Q4	Galactic	3
Perez	Q4	Galactic	6

This information can be summarized in a crosstab. Here is a crosstab that shows unit sales by printer for each quarter:

The sample crosstab has the heading " This report summarizes the unit sales of printers in each quarter. 11 / 9 / 98." Under the title are the headings Sum of Units and Quarter. Below them is a column heading for Product, a column heading for each quarter, and a grand total for each product row. At the bottom of the crosstab are grand totals for all products for the columns that represent each quarter. Data is show for three sample products, Cosmic, Galactic, and Stellar.

The first-quarter sales of Cosmic printers displays in the first data cell. (As you can see from the data in the Printer table shown before the crosstab, in Q1 Simpson sold 33 units, Jones sold 5 units, and Perez sold 26 units—totaling 64 units.) InfoMaker calculates each of the other data cells the same way.

To create this crosstab, you only have to tell InfoMaker which database columns contain the raw data for the crosstab, and InfoMaker does all the data summarization automatically.

What crosstabs do

Crosstabs perform two-dimensional analysis:

The first dimension is displayed as columns across the crosstab.

In the preceding crosstab, the first dimension is the quarter, whose values are in the Quarter column in the database table.
The second dimension is displayed as rows down the crosstab.

In the preceding crosstab, the second dimension is the type of printer, whose values are in the Product column in the database table.

Each cell in a crosstab is the intersection of a column (the first dimension) and a row (the second dimension). The numbers that appear in the cells are calculations based on both dimensions. In the preceding crosstab, it is the sum of unit sales for the quarter in the corresponding column and printer in the corresponding row.

Crosstabs also include summary statistics. The preceding crosstab totals the sales for each quarter in the last row and the total sales for each printer in the last column.

How crosstabs are implemented in InfoMaker

Crosstabs in InfoMaker are implemented as grid reports. Because crosstabs are grid reports, you can resize and reorder columns when you run the crosstab.

Running a crosstab You can run a crosstab by previewing it in the Report painter and by running it from an executable file.