Reader Poll: Should the axis for bar charts always start at zero?

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It all began with my Excel Dashboard Tutorial – Making a dashboard with player statistics. I have used bar charts with axis whose minimum is not zero, to create a dramatic effect in the charts. See below:

excel-barchart-rule-breaking

Jon Peltier commented saying that,

Rule #1: Bar and column chart value axes should start at zero. Since the lengths of bars and columns represent their values, starting at a position other than zero will lead to a misleading display.

As always Jon raised an excellent point. I liked it so much that I wanted to get your opinions on this axis scaling issue.

What do I think about this visualization rule ?

First the positive points about the rule:

  • If you start axis at non-zero values, it gives a wrong impression about the data. In my example above you might end up thinking the top value is actually 10 times that of bottom value.
  • The rule helps easy interpretation of data, since everything starts at zero.


Now the negative points about the rule:

  • Not all data starts at zero (like the above with values ranging from 8000 to 12000). So when you create a bar chart for the data (why only bar charts, because they are easy to make and read) often you end up creating charts from which making out any analysis could be slightly difficult
  • Breaking this rule helps in creating dramatic effect on your charts, one of the reasons we use them. Often when you use data with narrow range, creating dramatic effect could be difficult. Axis adjustments can help (you may want to try logarithmic axis scale as well)

Finally, I think this rule can be broken as long as we have right data and make alternative arrangements (like adding data labels) to ensure correct interpretation. Since this is a standard people have come to expect, it is better to make it clear to your audience about the axis range.

What do you think about the charting rule: Bar and column chart value axes should start at zero.

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13 Responses to “Data Validation using an Unsorted column with Duplicate Entries as a Source List”

  1. Vipul says:

    Pivot Table will involve manual intervention; hence I prefer to use the 'countif remove duplicate trick' along with 'text sorting formula trick; then using the offset with len to name the final range for validation.

  2. Rich says:

    if using the pivot table, set the sort to Ascending, so the list in the validation cell comes back alphabetically.

  3. Kieranz says:

    Hui: Brillant neat idea.
    Vipul: I am intrigued by what you are saying. Please is it possible to show us how it can be done, because as u said Hui's method requires user intervention.
    Thks to PHD and all
    K

  4. sam says:

    Table names dont work directly inside Data validation.
    You will have to define a name and point it to the table name and then use the name inside validation
    Eg MyClient : Refers to :=Table1[Client]
    And then in the list validation say = MyClient

  5. Vipul says:

    Kieranz,
    Pls download the sample here http://cid-e98339d969073094.skydrive.live.com/self.aspx/.Public/data-validation-unsorted-list-example.xls
    Off course there are many other ways of doing the same and integrating the formulae in multiple columns into one.

  6. Vipul says:

    Pls refer to column FGHI in that file. Cell G4 is where my validation is.

  7. Kieranz says:

    Vipul:
    Many thks, will study it latter.
    Rgds
    K

  8. [...] to chandoo for the idea of getting unique list using Pivot tables.  What we do is that create a pivot table [...]

  9. Playercharlie says:

    @Vipul:

    Thanks, that was awesome! 🙂

  10. Vipul says:

    @Playercharlie Happy to hear that 🙂

  11. Enrique says:

    Great contribution, Hui. Solved a problem of many years!

  12. FARIS says:

    Thanks to you, A LOT

  13. Mohamed says:

    Hi Hui,
    Greeting
    hope you are doing well.
    I'm interested to send you a private vba excel file which i need to show detail of pivot in new workbook instead of showing in same workbook as new sheet.

    Please contact me on muhammed.ye@gmail.com

    Best Regards

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