A bar graph or histogram is one of the most useful, simple, and popular techniques in graphic presentations. Bar graphs use vertical or horizontal bars to make comparisons between one or more ranges of data or to report frequencies (i.e., histogram). The length of each bar or of its components is proportional to the quantity or amount of each category represented. Bar
graphs are most useful for comparing the magnitude or size, of coordinate items or of parts of a total.
This bar graph compares the days per year with a temperature above 38 degrees Celsius for a selected city in the United States. Keep in mind that the main emphasis and purpose of simple bar graphs is to focus on comparative magnitudes. As with all graphs, the scale, scale lines, and ordering of categories should be considered based on the intent of the graph to communicate a particular message (e.g., persuade an audience, support a position, report a finding).
