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Re: empty cells in data tables

for

From: Trafford, Logan
Date: Feb 15, 2013 6:44AM

Thanks for this response and the link to your article. I'm trying to formulate policy for the large (gov't) organization I work for and it's essentially excel documents that report statistics where the issues lie. Your section on "Conventional notations in statistics" confirmed the direction I was heading in.

Thanks again.

Logan

-----Original Message-----
From: <EMAIL REMOVED> [mailto: <EMAIL REMOVED> ] On Behalf Of Jukka K. Korpela
Sent: February 14, 2013 4:25 PM
To: <EMAIL REMOVED>
Subject: Re: [WebAIM] empty cells in data tables

2013-02-14 22:42, Trafford, Logan wrote:

> What is the generally accepted best practice for dealing with large
> blocks of empty data cells in tables

Years ago, I wrote a treatise on empty cells, primarily to address some styling problems:
http://www.cs.tut.fi/~jkorpela/html/emptycells.html

It's a bit dusty, but I think the basic reasoning is still relevant: we should try to avoid leaving cells empty in data tables. It is not just a matter of nonvisual access, which may or may not have trouble with empty cells. In general, when a table cell is presented as empty, visually or otherwise, the question arises what the emptiness means. It can mean a wide variety of things, from simple oversight or data error to absence of data due to security restrictions, logical impossibility, lack of anything to report, or just lack of data.

Depending on the nature of the data and the table, as well as the human language, different notations can be used, and may need to be explained.
A fairly common convention is that an en dash indicates absence of data without disclosing a reason; but in some conventions, it indicates an exact value of zero.

> For example, suppose you have a report with 5 columns and 50 rows
> (each row represents a different building location for example). Now
> under one column, perhaps only 5 of the 50 buildings have a value
> associated with that category, while the other 45 do not.

In this case, en dashes might be suitable, possibly along with CSS settings that set e.g. the background of those cells to gray.

> Should the cell(s) be left blank, or should some kind of value be put
> in (like “nil”, “n/a” etc.)?

The dummy values, or metadata, to be used depends on the context. This often tricky, since the notations should be compact. The notation n/a or N/A is now used even when the language is not English, but this might not be suitable in documents for a general audience. Moreover, "n/a" is very ambiguous. "Not applicable" and "not available" can be very different things.

Yucca



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