HP 40gs - Manual (Page 117)

Statistics aplet 10-13
To define your
own fit
1. In Numeric view, make sure is set.
2. Display the Symbolic view.
3. Highlight the Fit expression ( Fit1, etc.) for the
desired data set.
4. Type in an expression and press .
The independent variable must be X, and the
expression must not contain any unknown variables.
Example:
.
This automatically changes the Fit type ( S1FIT, etc.) in
the Symbolic Setup view to User Defined.
Quadratic Fits to a quadratic curve,
y = ax
2
+bx+c. Needs at least
three points.
Cubic Fits to a cubic curve,
y = ax
3 +bx 2 +cx+d. Needs at least
four points.
Logistic Fits to a logistic curve,
,
where L is the saturation value for
growth. You can store a positive
real value in L, or—if L=0—let L
be computed automatically.
Exponent Fits to an exponent curve,
.
Trigonometric Fits to a trigonometric curve,
. Needs
at least three points.
User Defined Define your own expression (in
Symbolic view.)
Fit model Meaning (Continued)
y
L
1 ae
bx – ( )
+
-------------------------- =
y ab
x
=
y a bx c + ( ) sin ⋅ d + =
1.5 x cos × 0.3 x sin × +
hp40g+.book Page 13 Friday, December 9, 2005 1:03 AM