HP 39gs - Page 115

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–()
+
--------------------------
=
yab
x
=
ya bxc+()sin⋅ d+=
1.5 xcos× 0.3 xsin×+
HP 39gs English.book Page 13 Wednesday, December 7, 2005 11:24 PM