Scales on graphs

Discussion in 'All Things Boats & Boating' started by gonzo, Aug 16, 2017.

  1. gonzo
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    gonzo Senior Member

    On a different thread there has been some misunderstandings related to scales. A couple of members questioned why it makes a difference whether a scale is linear or logarithmic. I would like to discuss scale types and their advantages.
     
  2. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

    I am still trying to figure out how to use my slide rule. :(
     
  3. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

    At least it doesn't leave a carbon footprint. o_O
     
  4. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

    Seriously, I usually get a better perspective with a linear graph.
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    It depends on what is intended to be depicted. If the horizontal scale is half a mile long, and the vertical six inches high, some compression is required for it to be visually interpreted.
     
  6. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

    True, but I don't see compressed as logarithmic. Please correct me if I am misunderstanding.
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    If you want to give a fairly detailed picture of recent trends, set against a much broader picture of long term ones, then the scale has to be uneven, to be seen at a glance. So long as the scale change is clear, all good.
     
  8. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

    As long as the distortion is explained and not used to deceive, I am okay with it.
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    Of course, When I see a graph showing, e.g., how the Australian dollar has risen sharply, and it looks like it is on a zig-zag upward course at a 45 degree angle, it becomes rather less dramatic when you notice the vertical scale started at 75 cents US and peaks at 77 cents. Misleading.
     
  10. gonzo
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    gonzo Senior Member

    Logarithmic scales can be convenient. For example, the cooling of an object is a logarithmic function. However, it can be linearized with a logarithmic scale, which may make it easier to use.
     
  11. TANSL
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    TANSL Senior Member

    Logarithmic scales can be necessary, essential. To understand why you just have to read post # 7 of Mr Efficiency. That is the correct explanation. The rest are misconceptions.
     
  12. hoytedow
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    hoytedow Fly on the Wall - Miss ddt yet?

    Mercator projection is another good example of that.
     
  13. TANSL
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    TANSL Senior Member

    A lorithmic function can be represented on axes with linear scales. It has nothing to do the form of the function with the scale that is adopted to represent it.
    A straight line can be represented in logarithmic axes and in some cases there will be no choice but to do so.
    Do not confuse concepts.
     
  14. gonzo
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    gonzo Senior Member

    Do you understand how to linearize a graph? We do this with experimental data on a daily basis.
     

  15. TANSL
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    TANSL Senior Member

    Who are "we"?. You only can do it with experimental data?. Is it not possible to do it with data obtained from reality?.
    What a strange and most disturbing science!
     
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