When deciding how to arrange content in a table, consider:
- the amount of data
- the number of categories and number of sets of quantitative values
- the number of characters in each data cell for each category
- sequences and relationships in the data
- subsets or groupings within the data.
Tables can be structured in 2 main ways (see tables below):
- unidirectionally – categories are arranged in 1 direction, either across the columns or down the rows
- bidirectionally – categories are arranged in 2 directions, both across the columns and down the rows:
Unidirectional table with categories (cities) listed across the columns
Unidirectional table with categories (cities) listed down the rows
Bidirectional table with categories listed across the columns (gender) and down the rows (cities)
The categories themselves become the column or row headings.
When you are dealing with smaller tables (few categories and a small amount of data), there is more flexibility to arrange the data either way, although it is more conventional to arrange categories as column headings and list the data down the columns. If you have a large amount of data in each category, this may be your only option, because the table is then more likely to fit on a conventional page or screen.
Caution! Do not force a table with only a couple of columns to span an unnecessary width – this affects readability.
If you have a large number of categories but a small dataset for each, it may be best to arrange the categories as row headings and list the data across the table (see Use sequences to order your data).
If the data cells for some of your categories contain lengthy text, you may be better off restructuring the table by transposing the row and column headings. Then only some columns need to be wide, and text content will be easier to read, with a more appropriate column width:
Poor arrangement of data, resulting in narrow, difficult-to-read text columns
Considered arrangement of data, allowing column widths to be adjusted to suit the cell contents
Another issue to take into account is which orientation will ensure that comparable sets of data appear close to each another. Also, screen readers will read a table from left to right across each row (see Making tables accessible), so consider how this will work with your data layout.
