# Fundamentals of Graphing – Interactive tutorial

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## Discussion

Column (vertical bars), bar (horizontal bars), pie, and doughnut graphs are designed for categorical types of independent variables. Categorical variables are distinct groupings that have no intermediate values. Some examples of categories are species, cities, and treatment groups. Authors of research papers often use vertical column charts to present categorical data. The other plot types listed above are seldom if ever used in a scientific context. NOTE: Excel distinguishes column from bar graphs, while many authors use the terms column and bar interchangeably to refer to a graph with vertical columns.

Line, XY (scatter), and area graphs are designed to present parametric variables. A parametric variable has a numeric value that can be plotted on a scale. Parametric variables can be continuous, as with time or temperature, or can be discrete. Examples of a discrete parametric variable are numbers of individuals in a population, or levels in a preference survey (e.g., on a scale of 1 to 5...).

In Excel, a line graph is designed to plot one or more continuous dependent variables versus a discrete independent variable. A scatter plot is designed to plot one or more continuous dependent variables versus a continuous independent variable. An area (stacked area) plot is designed to display the relative contribution of each dependent variable over time or categories.

If you wish, you may change your answer(s) before continuing to the next window.

column
bar
line
pie
XY (scatter)
area
doughnut
other

## Previous conclusions

Time is the independent variable, to be plotted on the x axis; height (a measured quantity) is a dependent variable, to be plotted on the y axis.

Weekly height measurements for seedlings of Acer palmatum:

 week 0 2 4 6 8 10 12 measured 1.2 1.4 1.4 1.9 5.8 5.7 5.3 heights 0.3 0.5 2.0 3.0 2.9 4.8 5.1 in inches 1.1 1.0 2.3 3.8 4.9 4.8 8.5 1.1 1.7 2.2 2.6 3.7 8.2 8.2 1.0 1.8 2.4 3.5 5.6 6.1 7.0 1.5 2.2 2.0 2.3 4.8 4.8 5.5 1.3 1.5 2.0 3.1 1.1 8.3 5.6 0.8 1.5 2.1 3.1 4.6 6.1 2.2 1.7 1.7 2.5 4.3 4.2 7.4 4.8 1.5 1.6 1.6 5.0 5.1 3.7 8.4 1.6 1.2 2.7 1.8 3.8 4.3 4.3 1.1 1.2 1.5 2.8 7.4 4.3 5.9