user manual

Statistics 12-27
8312STAT.DOC TI-83 international English Bob Fedorisko Revised: 02/19/01 12:42 PM Printed: 02/19/01 1:37
PM Page 27 of 38
PwrReg (power regression) fits the model equation y=ax
b
to
the data using a least-squares fit and transformed values
ln(x) and ln(y). It displays values for
a and b; when
DiagnosticOn is set, it also displays values for r
2
and r.
PwrReg [
Xlistname
,
Ylistname
,
freqlist
,
regequ
]
Logistic fits the model equation y=c / (1+a
ä
e
L
bx
) to the data
using an iterative least-squares fit. It displays values for
a, b,
and
c.
Logistic [
Xlistname
,
Ylistname
,
freqlist
,
regequ
]
SinReg (sinusoidal regression) fits the model equation
y=a sin(bx+c)+d to the data using an iterative least-squares
fit. It displays values for
a, b, c, and d. At least four data
points are required. At least two data points per cycle are
required in order to avoid aliased frequency estimates.
SinReg [
iterations
,
Xlistname
,
Ylistname
,
period
,
regequ
]
iterations
is the maximum number of times the algorithm
will iterate to find a solution. The value for
iterations
can
be an integer
‚
1 and

16; if not specified, the default is 3.
The algorithm may find a solution before
iterations
is
reached. Typically, larger values for
iterations
result in
longer execution times and better accuracy for
SinReg, and
vice versa.
A
period
guess is optional. If you do not specify
period
, the
difference between time values in
Xlistname
must be equal
and the time values must be ordered in ascending
sequential order. If you specify
period
, the algorithm may
find a solution more quickly, or it may find a solution when
it would not have found one if you had omitted a value for
period
. If you specify
period
, the differences between time
values in
Xlistname
can be unequal.
Note:
The output of
SinReg
is always in radians, regardless of the
Radian/Degree
mode setting.
A SinReg example is shown on the next page.
PwrReg
(ax
b
)
Logistic
c/(1+a
ä
e
L
bx
)
SinReg
a sin(bx+c)+d