These values cannot be omitted for the correct calculation for a polynomial trend. known_x's (optional) are independent data values:.

known_y's (required) are dependent data values,.

To work with this function for polynomial trends, just use the indicated powers of the known_x's instead of known_x's: To calculate the polynomial trendline values, Excel offers the array function TREND () (see the notes above about array functions) that returns values along a linear trend. Now the variable y does not depend on one variable x in n different degrees but on n independent variables X i.Įxcel offers the following functions to calculate the trend parameters:Ĭalculating the polynomial trendline values After changing the variables to X i = x i, the calculations are completely similar to the linear case y = a n*X n +. + a 3*x 3 + a 2*x 2 + a 1*x + b is transformed to a linear function using a change of variables. Note: Excel uses a linear model: the polynomial function y = a n*x n + . Excel works with polynomial orders from 2 nd to 6 th.

n is the degree of the polynomial (in Excel, the order of a polynomial).

, a 3, a 2, a 1 and b are calculated parameters of the function (also named function coefficients or constants) that describe the relationship between x and y, The polynomial trendline is a curved line with the function:

Polynomial trendline equation and formulas

a dependent or response variable y (named as known_y's).

an independent, predictor, or explanatory variable x (named as known_x's),.

The degree of the polynomial is specified in the Order field - see more about the polynomial trendline in Excel.Įxcel uses the least squares method to fit a polyline for the data points.įor a trend line, two sets of variables are required:

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