ABSTRACT
A graph shows the relationship between two variables. Graphical representation is a quick and easy way to show the information collected from a test or an observation. The shape of a graph depends on the data being plotted and helps us to draw conclusions. Figure 8.1 shows four typical graphs that we may come across in construction and engineering.
A graph consists of two axes drawn at right angles to each other. The horizontal line is called the x-axis and the vertical line is called the y-axis. The point where the axes intersect is called the origin, and at this point the values of x and y are zero. The axes are known as rectangular or Cartesian axes, as shown in Figure 8.2.
