Microsoft Office Tutorials and References
In Depth Information
Power trendline
Figure 5-11: A chart displaying a logarithmic trendline
Power trendline
A power trendline describes data that increases (or accelerates) at a specific rate. A
power law trendline appears as a straight line on a chart with a logarithmic y-axis
and a logarithmic x-axis scale. This trendline is limited to positive values. The
equation for a power trendline looks like this:
y = c * x^b
Figure 5-12 shows a chart with a power trendline added. Cell E2 contains the
following formula, which calculates c:
=EXP(INDEX(LINEST(LN(B2:B11),LN(A2:A11)),1,2))
The value for b is calculated in F2, using this formula:
=INDEX(LINEST(LN(B2:B11),LN(A2:A11)),1)
Column C shows the predicted y values for each value of x, using the calculated
values for b and c. For example, the formula in cell C2 is
=$E$2*(A2^$F$2)
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