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CH 1  Avoid manipulated axes


Charts serve as a means to visually compare numerical values. Manipulated axes defeat this purpose of explaining actual interrelations.


CH 1.1  Avoid truncated axes

Charts with value axes not starting at zero (“cut” axes) are not "wrong" in and of themselves, but the message to be visually conveyed then does not correspond to the numerical values upon which the chart is based. Therefore, value axes should generally start at zero, see figure SUCCESS rule CH 1.1.


One exception to this rule exists: charts with indexed data (e.g. if the value for the index period is set to 100%) with only small variances from 100%. Here “zooming in” on the variances could be of greater value than indicating the absolute values (starting at zero). In this case, position the category labels at the 100% line in order to avoid misinterpretations.


CH 1.2  Avoid logarithmic axes

Avoid logarithmic scales because they do not allow the visual comparison of values, see figure SUCCESS rule CH 1.2. In business, very few applications for logarithmic axes exist (e.g. comparing growth rates of different stocks in percent).


CH 1.3  Avoid different class sizes

If the categories represent ordered classes of elements (e.g. age classes) as used for the visualization of distributions in histograms, use class sizes of identical width (e.g. ten years). Otherwise, true visual comparability is impossible, see figure SUCCESS rule CH 1.3.




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