4.50 Table
A table is a float object. Tables inherit all the caveats applicable to float objects. The table command calls a hold-all environment or a container to hold other data structures. It is the basic structure of data presentation in any organized form. The only parameter it takes is the placement parameter. The table environment is native to LaTex; it does not need to be specifically invoked. The usual structure of initiating the table environment is

Having set up a table environment at the top-most level, the underlying data and design considerations determine the type of sub-environments. For instance, the array environment is best suited for number-heavy data or scientific notations, because it accommodates maths mode. Tabular and Tabularx are two instances of text-dominant data presentations. The difference between the two is discussed later in section 4.53.1 and associated illustration.

4.51 Arrays: An array is an organised presentation of numbers and maths entries. This is important because the array command works only in the maths mode. An array environment is invoked with the command \begin {array}. But prior to calling the array environment, we have to invoke the maths mode with \[ or a $. Also, it is usual to center arrays and tables in the middle of the page with a \begin{center} prior to getting into the main array environment.

The array environment allows for data in multi-column structures to be aligned in a manner that the presentation is aesthetically pleasing and the data can be assimilated without ambiguity. The alignment for each column in a multi-column array is specified at the invocation of the array environment itself like so: \begin{array}{x}, where {x} is a column specifier which can take one of three options:

• l: left aligned column


• r: right aligned column


• c: centered (within column)

Once the structure is specified, data is input line-wise, with fields separated with a &, like so for a three column array: 'Left entry & center entry & right entry\\'. The two backslashes have the usual effect of introducing a line break. The code below produces the output in Figure 4.51



4.52 Tabular
The data structure in this sub-section is tabular and not table. The difference is profound.

The array environment (sub-section 4.51) is a data structure in the maths mode to store numbers. The tabular environment on the other hand is for text data, which means it has all the commands and accompaniments that are needed for the proper display of text data. Beyond that, the rest of the steps in setting up the text structure are the same.

Figure 4.52 illustrates the page output from the code snippet below.

Figure 4.52 Tabular environment, with fixed width columns

4.53 Tabularx
Tabularx is not a derivative of tabular. It is not an alternative for all seasons and all reasons. It is actually the tabular environment plus plus, designed for greater user control over the table output. It loads the array package at start, bringing the added flexibility of dealing with tables, column widths and column headers.

Here is a quick comparison.

The tabularx command takes only one parameter, the desired width of the table, as per page design considerations. As discussed later, the tabularx engine adjusts column widths to fit the columns to the overall table width. The tabularx environment is called as under:

\begin{tabularx}{\textwidth}

This sets the table width to fit the exact text width. Design specifications of 0.80\textwidth or 0.50\textwidth will output tables of fixed size, so that the user can place the other design elements around the table, without concerns of overlap or white spaces. In academic papers with two- column formats and a gutter, the table has to be set within the exact specs of the column text width. So also, in in the book or report documentclass where the tables are set to fit the pagewidth.
The Figure 4.53.0 below illustrates the stretch mechanism which returns equally spaced columns. The three tables are set at 70%, 85% and 100% of text width.



The tabularx package modifies the basic p column type (column with width specification) into a new column type called X. The tabularx call has two parameters:

• The overall width of the intended table;


• The specs of the columns within.

A typical call with the X column is reported in line 7 of the tabularx code:

\begin{tabularx}{\textwidth}{XXXX}

In Figure 4.53.1 (right column, below), line 7, the table is set for 100% of the text width; four columns are specified, each of type x.

The use of the X column specification instructs the compiler to automatically calculate the widths of each of the X columns to add up to the overall target width. It follows, therefore, that each tabularx call must have one x column. Since the width of all x columns is compiler-calculated, all x columns will have the same width.

In a mixed column specification, this calls for serious consideration: the tabularx distributes the white space not needed by columns of fixed width is distributed evenly to the columns of type x.

In tabular, on the other hand, the table width is determined by the compiler to best suit the available text/column contents.

Tabularx, with its internal stretch mechanism, returns a common column width for all columns despite differences in column contents. This leaves lots of white spaces, lending an open look to the table. Design gurus prefer this open look to the ruled and boxed look of earlier decades.
     o However, there may be occasions to prefer compactly designed tables, and the choice of tabular environment.
The code snippet and the output Figure 4.53.1 below illustrate the differences between tabular and tabularx.

Figure 4.53.1: Column widths in tabular and tabularx environments

4.54 Tabularx*:
The tabularx* command works on the table columns by changing the inter-column whitespace. This is a fine design consideration. The tabularx* call compares with the tabularx call which works by changing the column widths. In practice, the two environments can produce fairly similar looking results in some cases and rather different results in others.