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Sinusoidal Graphs

Part 4: Fitting Sinusoidal Graphs to Data

  1. The following table shows average temperature per month for Tamanrasset, Algeria (near the Sahara Desert). Temperature and rainfall data for this and other places can be found at the World Climate site.
  2. Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
    °F 55.0 59.7 65.1 72.0 79.0 83.8 83.3 82.8 79.9 72.7 64.0 56.7

    Plot the data and observe that they appear roughly sinusoidal. Why does it make sense that average monthly temperature can be modelled by a periodic function?

  3. We're going to model this graph with a sinusoidal function. Looking at the data plot, estimate the period, amplitude, and vertical and horizontal translations. Use those values in a sinusoidal equation, and test your model by graphing it on top of the data. (It won't be exact, but it should at least hit some of the points and be relatively close to the others.)
  4. Go to the World Climate site, and select temperature values for another city. One place with interesting data is Vostok, Antarctica. Plot the data, and try to fit them with a sinusoidal model. (Note: The rainfall data, while interesting, generally does not fit comfortably into a sinusoidal model.)
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modules at math.duke.edu Copyright CCP and the author(s), 1998