Graphs & Diagrams

• Pie Charts: These represent data as segments of a circle to show the proportion of a whole; the total must always equal 100% or $360^\circ$.

• Rose Diagrams: These use multidirectional axes (often based on compass points) to plot data like wind direction or noise levels using bars extending from a central point.

• Triangular Graphs: These feature three axes, each ranging from 0 to 100%, used to plot data that can be divided into three components (e.g., soil composition of sand, silt, and clay).

• Line Graph vs. Cross-Section: A standard line graph shows a variable changing over time, whereas a cross-section (like a river profile) uses a line to show the physical shape of a feature at a specific point in space.

• Percentage Change: To calculate the relative change between two values, use the formula:

$\text{Percentage Change} = \frac{\text{New Value} - \text{Old Value}}{\text{Old Value}} \times 100$

• Pie Chart Angles: To find the degree of a segment from a percentage, divide the percentage by 100 and multiply by 360:

$\text{Degrees} = \frac{\%}{100} \times 360^\circ$

• Completing Graphs: Exams often require finishing a partially drawn graph; always use the same style (e.g., bar width or line thickness) as the existing elements.

• Identifying Anomalies: Look for data points that fall significantly outside the general trend or line of best fit; these should be noted as potential errors or unique occurrences.

• Scale Awareness: Always check the axes for 'broken' scales or non-zero starts, as these can intentionally or accidentally mislead the reader about the magnitude of change.