Visualizing Trends means in many cases either Time Series Chart (can you spot a pattern here with your naked eye?):
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or Motion Chart (both best done by ... Google, see it here http://visibledata.blogspot.com/p/demos.html ) - can you predict the future here(?):
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or Sparklines (I like Sparkline implementations by Qlikview and Excel 2010) - sparklines are scale-less visualization of "trends":
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may be Scatter (Excel is good for it too):
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and in some cases Stock Chart (Volume-Open-High-Low-Close, best done with Excel) - for example Microsoft stock is fluctuating near the same level for many years, so I guess there is no visible trend here, which may be spells a trouble for Microsoft future (compare with visible trend of Apple and Google stocks):
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Or you can see Motion, Timeline, Sparkline and Scatter charts alive/online below: for Motion Chart Demo, please Choose a few countries (e.g. check checkboxes for US and France) and then Click on "Right Arrow" button in the bottom left corner of the Motion Chart below:
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In statistics trend analysis often refers to techniques for extracting an underlying pattern of behavior in well-ordered dataset which would otherwise be partly hidden by "noise data". It means that if one cannot "spot" a pattern by visualizing such a dataset, then (and only then) it is time to apply regression analysis and other mathematical methods (unless you smart or lucky enough to remove a noise from your data). As I said in a beginning: try to see it first! However, extrapolating the past to the future can be a source for very dangerous mistakes (just check a history of almost any empire: Roman, Mongol, British, Ottoman, Austrian, Russian etc.)