SPSS® 12.0 Command Syntax Reference

Operations
NLR 1047
• By default, the predicted values, residuals, and derivatives are created as temporary variables.
To save these variables, use the SAVE subcommand.
Weighting Cases
• If case weighting is in effect, [C]NLR uses case weights when calculating the residual sum
of squares and derivatives. However, the degrees of freedom in the ANOVA table are
always based on unweighted cases.
• When the model program is first invoked for each case, the weight variable’s value is set
equal to its value in the working data file. The model program may recalculate that value.
For example, to effect a robust estimation, the model program may recalculate the weight
variable’s value as an inverse function of the residual magnitude. [C]NLR uses the weight
variable’s value after the model program is executed.
Missing Values
Example
Cases with missing values for any of the dependent or independent variables named on the
[C]NLR command are excluded.
• Predicted values, but not residuals, can be calculated for cases with missing values on the
dependent variable.
• [C]NLR ignores cases that have missing, negative, or zero weights. The procedure displays
a warning message if it encounters any negative or zero weights at any time during its
execution.
• If a variable used in the model program or the derivatives program is omitted from the
independent variable list on the [C]NLR command, the predicted value and some or all of
the derivatives may be missing for every case. If this happens, SPSS generates an error
message.
MODEL PROGRAM A=.5 B=1.6.
COMPUTE PRED=A*SPEED**B.
DERIVATIVES.
COMPUTE D.A=SPEED**B.
COMPUTE D.B=A*LN(SPEED)*SPEED**B.
NLR STOP.
• MODEL PROGRAM assigns values to the model parameters A and B.
• COMPUTE generates the variable PRED to define the nonlinear model using parameters A
and B and the variable SPEED from the working data file. Because this variable is named
PRED, the PRED subcommand is not required on NLR.
• DERIVATIVES indicates that calculations for derivatives are being supplied.