Adds terms to, or drops them from a linear, generalized linear, generalized additive or nonlinear model.
|What to print (
||How to treat nonlinear parameters between groups (
||How to treat the constant (
||Limit for expansion of model terms; default
||Whether to pool ss in accumulated summary between all terms fitted in a linear model (
||Whether to base ratios in accumulated summary on rms from model with smallest residual ss or smallest residual ms (
||Which warning messages to suppress (
||Printing of probabilities for variance and deviance ratios (
||Printing of probabilities for t-statistics (
||Statistics to be displayed in the summary of analysis produced by
||Probability level for confidence intervals for parameter estimates; default 0.95|
||Description for line in accumulated analysis of variance (or deviance) table when
|formula||List of explanatory variates and factors, or model formula|
SWITCH modifies the current regression model, which may be linear, generalized linear, generalized additive, standard curve or nonlinear. Terms in the specified formula are dropped from the current model if they are already there, or are added to it if they are not. It is best to give a
TERMS statement before investigating sequences of models using
SWITCH, in order to define a common set of units for the models to be explored. If no model is fitted after the
TERMS statement, the current model is taken to be the null model.
If the current model contains a smoothed term (specified e.g. by
LOESS) which is included in the formula specified by the parameter of
SWITCH with a different number of degrees of freedom (or with the smoothing parameter set),
SWITCH will then refit the smoothed term.
The model fitted by
SWITCH will include a constant term if the previous model included one, and will not include one if the previous model did not. You can, however, change this using the
The options of
SWITCH are the same as those of the
FIT directive, but with the extra
NONLINEAR option which controls whether separate nonlinear parameters are fitted to different groups when fitting curves, as in
TERMS statement was given before fitting the model, any restrictions on the variates or factors in the model will have been implemented then. So any restrictions on vectors involved in the model specified by
SWITCH will be ignored. If no
TERMS statement has been given and
SWITCH introduces new terms into the model, restrictions on the variates or factors in these terms will be taken into account and may cause the units involved in the regression to be redefined.
Commands for: Regression analysis.
" Examples 2:3.2, 2:3.2.1-6, 2:3.2.7a-b, 2:3.2.8 " " Multiple linear regression of the heat given out by setting cement on four chemical constituents. Data from Woods, Steinour & Starke (1932); analysed by Draper & Smith (1981) p.629." OPEN '%GENDIR%/Examples/GuidePart2/Cement.dat'; CHANNEL=2 READ [PRINT=data; CHANNEL=2] X[3,1,4,2],%gypsum,Heat " Analyse only those samples with 3.2% gypsum." RESTRICT Heat; %gypsum==3.2 MODEL Heat " Constituents are: X tricalcium aluminate X tricalcium silicate X tetracalcium aluminoferrite X beta-dicalcium silicate " FIT [FPROBABILITY=yes; TPROBABILITY=yes] X RDISPLAY [PRINT=accumulated; FPROBABILITY=yes] RKESTIMATES X; ESTIMATES=Est[1...4]; SE=se[1...4] PRINT Est,se,Est,se,Est,se,Est,se; FIELD=10,8 TERMS [PRINT=correlation] X ADD [PRINT=deviance,estimates; TPROBABILITY=yes] X[1,2,4] DROP [PRINT=deviance,estimates; TPROBABILITY=yes] X SWITCH [PRINT=estimates,accumulated; FPROBABILITY=yes;\ TPROBABILITY=yes] X[2,4] TRY X[2,3] FIT [FPROBABILITY=yes; TPROBABILITY=yes] X RWALD FIT [PRINT=*] X STEP [INRATIO=4; OUTRATIO=4; FPROBABILITY=yes; TPROBABILITY=yes] X[1...4] TERMS X STEP [PRINT=changes; INRATIO=4; OUTRATIO=4; MAXCYCLE=10] X RDISPLAY [FPROBABILITY=yes; TPROBABILITY=yes] RSEARCH [METHOD=allpossible] X[1...4] CLOSE 2