Logarithmic Regression (LnReg) |
|
Characteristics:
• The scatter plot appears to resemble the shape of the function y = ln( x).
• Form: y = a + b ln( x)
• The calculator takes the natural log of the x-coordinates and then preforms a linear regression. Thus any x-coordinate that is negative or zero will cause an ERR DOMAIN on the calculator.
|
|
• The logarithmic regression equation will be used to predict y-values that lie inside (interpolate) or outside the plotted values (extrapolate).
• Like the exponential function, the logarithmic function can be transformed to be a linear based regression.
Logarithmic regressions are widely used to model environmental data.
|
Sinusoidal Regression (SinReg) |
 The mathematical sinusoidal function and
the calculator's sinusoidal regression equation are slightly different.
Mathematical
Sinusoidal Function
y = Asin(B(x - C) + D
| A | = amplitude
B = frequency
period = 2π / B
D = vertical shift
C = horizontal shift
(called phase shift when B = 1) |
Calculator's
Sinusoidal Regression Equation
y = asin(bx + c) + d
| a | = amplitude
b = frequency
period = 2π / B
d = vertical shift
c / b is the horizontal shift
(right if c < 0 and left if c > 0)
|
|
|
Characteristics:
• The scatter plot appears to resemble a sine or cosine curve.
• Form: y = a sin(bx+c) + d
|
| • Notice that there is no correlation coefficient, r, or coefficient of determination, r2, listed for this regression. |
