One step further
markr wrote:The plot should look like a sine wave. Can you determine the amplitude, period, phase shift, and y offset so that you can come up with something that looks like:
y = A*sin(B*x+C)+D
That's the general form of the equation. Here's how to estimate the constants.
A is the amplitude of the wave. You can estimate it by taking the difference between the highest and lowest Y values and dividing by two.
D is the mean value. Estimate it by taking the mean value.
-C is the X value (time) where the curve crosses the mean from low to high. This looks like 11:00 in your data. Note the negative sign.
B is harder. You find it by taking 2PI divided by the amount of time it takes to complete one full cycle. You don't have one full cycle in your data, so use PI divided by the time it takes to go from the maximum value to the minimum value.
From the clues above, you should be able to get an equation and approximate the level on a new time. The cosine equation can be determined from the sine equation. Cos(x)=Sin(pi/2 - x), so use the same A and D from above and the relationship above to change the sine into the cosine.
Good luck
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