TI-Nspire™ Reference Guide 75
PowerReg
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PowerReg X,Y [, Freq] [, Category, Include]]
Computes the power regression y = (a·(x)
b
) on lists X and Y with
frequency Freq. A summary of results is stored in the stat.results
variable. (See page 97.)
All the lists must have equal dimension except for Include.
X and Y are lists of independent and dependent variables.
Freq is an optional list of frequency values. Each element in Freq
specifies the frequency of occurrence for each corresponding X and Y
data point. The default value is 1. All elements must be integers | 0.
Category is a list of numeric or string category codes for the
corresponding X and Y data.
Include is a list of one or more of the category codes. Only those data
items whose category code is included in this list are included in the
calculation.
For information on the effect of empty elements in a list, see “Empty
(void) elements” on page 131.
Output variable Description
stat.RegEqn
Regression equation: a·(x)
b
stat.a, stat.b Regression coefficients
stat.r
2
Coefficient of linear determination for transformed data
stat.r Correlation coefficient for transformed data (ln(x), ln(y))
stat.Resid Residuals associated with the power model
stat.ResidTrans Residuals associated with linear fit of transformed data
stat.XReg List of data points in the modified X List actually used in the regression based on restrictions of Freq,
Category List, and Include Categories
stat.YReg List of data points in the modified Y List actually used in the regression based on restrictions of Freq,
Category List, and Include Categories
stat.FreqReg List of frequencies corresponding to stat.XReg and stat.YReg
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