To calculate the exponential and logarithmic fit, the amount or response scales are transformed using the ln() function. The linear curve fit and the weight factors are applied to the transformed data, and the curve is calculated on the transformed data.
The Include origin and Force origin options are not valid due to the singularity of the ln() function at the origin.
Curve formula:
y = a * ln(x) + b
Transformations: The x scale is transformed.
x' = ln(x); y' = y
y' = a * x' + b
Curve formula:
y = b * ea * x
Transformations: The y scale is transformed.
x' = x; y' = ln(y)
y' = ln(b) + a*x'
To calculate the log/log fit, both amount and response scales are transformed using the log() function. The linear curve fit and the weight factors are applied to the transformed data, and the curve is calculated on the transformed data.
The Include origin and Force origin options are not valid due to the singularity of the log() function at the origin.
Curve formula:
log(y) = a * log(x) + b
Transformations: The x and y scales are transformed.
x' = log(x); y' = log(y)
y' = a * x' + b