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Graphs An Introduction

Graphs An Introduction. What is a graph?. A graph is a visual representation of a relationship between, but not restricted to, two variables.

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Graphs An Introduction

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  1. GraphsAn Introduction

  2. What is a graph? A graph is a visual representation of a relationship between, but not restricted to, two variables. A graph generally takes the form of a one- or two-dimensional figure. Although, there are three-dimensional graphs available, they are usually considered too complex to understand easily. A graph commonly consists of two axes called the x-axis (horizontal) and y-axis (vertical). A graph can show Discrete or Continuous data types. Data types determines which graph to use.

  3. Discrete or Continuous Discrete: Data that can be separated by some interval, for example: Recording the shoe sizes of a class – Bar graph Continuous: When data collected is continuous, for example: Recording temperature – Line graph

  4. This is a graph 25 Y – axis Scale or Increments 20 All graphs (except Pie Chart) have common elements: • Axis x and y (also z in 3D graphs) • Axis labels • A title • Scales or Increments • Can represent negative values 15 Y – axis label 10 5 Origin – does not always have to start at 0,0 X-axis 10 20 30 40 50 -20 -10 X-axis label -5 Scale or Increments -10

  5. If we draw a vertical line from any point on the x-axis Co-ordinates 25 Y – axis and a horizontal line from the y-axis 20 A (3,15) the point at which they meet gives us the co-ordinate 15 B (-4,10) 10 5 1 2 3 4 5 -5 -4 -3 -2 -1 -5 X-axis -10 -15 C (-5,-15) Back

  6. Types of Graphs Four basic types of graph or chart Line Pie Bar Scatter

  7. See creating a line graph presentation Line Graphs A good method of showing the relationship between two variables Back

  8. Bar Chart / Graph Used to compare values in a category or between categories. The graph shown here makes a visual comparison of the fat content of types of cheese

  9. Bar Chart / Graph Can be useful to study trends over time

  10. See creating a bar graph presentation Bar Chart / Graph Multiple (or group) bar graphs compare relationships of closely related sets Back

  11. See creating a pie chart presentation Pie Charts A pie chart is used to show how a part of something relates to the whole. This kind of graph is particularly suited to showing percentages Back

  12. Weight (kg) Height (cm) Scatter Graph Drawing a scatter graph is similar to drawing a line graph in that co-ordinates are used to plot the points. There are usually more points to be plotted in a scatter graph and the points can be in groups, therefore it is not possible to draw a line through all of the points. A scatter graph shows how much correlation there is between two variables that you suspect may be linked for instance height and weight as shown here: It is sometimes useful to draw a “line of best fit” to show the trend Line of best fit Back

  13. Summary A good graph: Accurately shows the data Grabs the reader's attention Has a title and labels Is simple and uncluttered Clearly shows any trends or differences in the data Is visually accurate (i.e., if one data value is 25 and another 50, then 50 should appear to be twice the size of 25).

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