Reference Guide

Full Command and Function Reference 3-177
PREDY
Type: Command
Description: Predicted y-Value Command: Returns the predicted dependent-variable value y
dependent
, based on
the independent-variable value x
independent
, the currently selected statistical model, and the current
regression coefficients in the reserved variable ΣPAR.
The value is predicted using the regression coefficients most recently computed with LR and
stored in the reserved variable ΣPAR. For the linear statistical model, the equation used is this:
y
dependent
= (mx
independent
) + b
where m is the slope (the third element in ΣPAR) and b is the intercept (the fourth element in
ΣPAR).
For the other statistical models, the equations used by PREDY are listed in the LR entry.
If PREDY is executed without having previously generated regression coefficients in ΣPAR, a
default value of zero is used for both regression coefficients–in this case PREDY will return 0 for
statistical models LINFIT and LOGFIT, and error for statistical models EXPFIT and PWRFIT.
Access: …µ PREDY
Input/Output:
Level 1/Argument 1 Level 1/Item 1
x
independent
→
y
dependent
Example: Given four columns of data in ΣDAT, the command sequence:
2 XCOL 4 YCOL PWRFIT LR 11 PREDY
sets column 2 as the independent variable column, sets column 4 as the dependent variable
column, and sets the power statistical model. It then executes LR, generating intercept and slope
regression coefficients, and storing them in ΣPAR. Then, given an independent value of 11, it
returns a predicted dependent value based on the regression coefficients and the statistical model.
See also: COLΣ, CORR, COV, EXPFIT, ΣLINE, LINFIT, LOGFIT, LR, PREDX, PWRFIT, XCOL,
YCOL
PREVAL
Type: Function
Description: With respect to the current default variable, returns the difference between the values of a
function at two specified values of the variable.
PREVAL can be used in conjunction with INTVX to evaluate definite integrals. See the example
below.
Access: Calculus, !Ö DERIV . & INTEG L.
Input: Level 3/Argument 1: A function.
Level 2/Argument 2: The lower bound.
Level 3/Argument 1: The upper bound.
The bounds can be expressions.
Output: The result of the evaluation.
Flags: Exact mode must be set (flag –105 clear).
Numeric mode must not be set (flag –3 clear).
Radians mode must be set (flag –17 set).
Example: Evaluate the following:
x
3
3 x + ( ) xd
0
3
∫
Command: PREVAL(INTVX(X^3+3*X),0,3)