WellCAD Basics - Advanced Logic Technology

1.8.4 Adding Regression
1.8.4.1 Regression Types
BOOK 1 - WELLCAD BASICS - 219
You can add regression lines to the cross-plot chart, individual plots, classified
points or a data cluster. To do so:
� Select Edit > Add Regression from the menu. The Regression Settings
dialog box opens.
Regression Settings dialog box
In the Type tab you can set a title identifying the regression object or WellCAD will
add a default title for you.
If you click on the drop down control for the regression Type you will get a list of
supported regression options. Together with the different fitting Criteria you will
have the following regression options:
� Linear fit (Y on X, X on Y and RMA (Reduced Major Axis)).
Calculates the least squares fit for a line represented by the formula:
y � mx � b
where m is the slope and b is the intercept.
� Second, Third and Fourth order Polynomial fit (Y on X and X on Y).
Calculates the least squares fit through points by using the following equation:
where b and c1 … c4 are constants.
2 3
y � b � c1x
� c2
x � c3x
�
c
4
x
4