Microsoft Office Tutorials and References

In Depth Information

**Polynomial trendline**

Figure 5-13: A chart displaying an exponential trendline

Polynomial trendline

A polynomial trendline defines a curved line and describes data that fluctuates in

an orderly pattern. When you request a polynomial trendline, you also need to

specify the order of the polynomial (ranging from 2 through 6). The equation for a

polynomial trendline depends on the order of the polynomial.

SECOND-ORDER TRENDLINE

A second-order trendline (also known as a quadratic trendline) describes data that

resembles a
U
or an inverted
U. Following is the equation for a second-order

polynomial trendline:

y = (c2 * x^2) + (c1 * x^1) + b

Notice that there are two c coefficients (one for each order).

Figure 5-14 shows a chart with a second-order polynomial trendline added.

Formulas entered in E2:G2 calculate the values for each of the c coefficients and

the b constant. The formulas are as follows:

E2:

=INDEX(LINEST(B2:B11,A2:A11^{1,2}),1)

F2:

=INDEX(LINEST(B2:B11,A2:A11^{1,2}),1,2)

G2:

=INDEX(LINEST(B2:B11,A2:A11^{1,2}),1, 3)