Sorry for my faulty email and another correct email I thank those who helped to solve a error in stepwise regression with missing values.
A good solution that I have tried was Andreas's advice. ===================================================================== Try data<-na.omit(original database) before you run step() or stepAIC() Kum On Tue, Feb 16, 2010 at 8:09 PM, Peter Ehlers <ehl...@ucalgary.ca> wrote: > > On 2010-02-16 1:24, Kum-Hoe Hwang wrote: >> >> Howdy, R Grues >> >> I have enjoyed R, but I cannot solve one problem easily. Please help my >> problem. >> When I tried the R script, I got the following Error. This error >> results from input data file exported through a Excel spreadsheet >> software. >> >> Error in step(lm(pop.rate ~ as.numeric(year) + as.factor(policy) + >> as.numeric(nation.grant) + : >> number of rows in use has changed: remove missing values? >> >> Could you direct me to solve the Error? >> Thanks in advance, > > This is a common situation when you use step() on data where > the predictors have missing values. > > A case (row) is included in the model only if all the > predictors for that model are non-missing for the case. > > As you vary which predictors are to be in the model, the > included cases will vary, resulting in models based on > different data. (Think of your cases as subjects; you want > all your models to be based on the same set of subjects.) > > Finally: (Re-)read the help page and note the 'warning'. > > -Peter Ehlers > >> >> >>> ############### outputs from R console ############### >>> pop<- step( >> >> + lm(pop.rate ~ as.numeric(year) + as.factor(policy) + >> as.numeric(nation.grant) >> + + as.numeric(do.grant) + as.numeric(city.grant) + >> as.numeric(DMZ.dist) + as.numeric(Seoul.dist), data=borderI.data, >> na.action = na.omit) >> + ) >> Start: AIC=494.27 >> pop.rate ~ as.numeric(year) + as.factor(policy) + as.numeric(nation.grant) + >> as.numeric(do.grant) + as.numeric(city.grant) + as.numeric(DMZ.dist) + >> as.numeric(Seoul.dist) >> Df Sum of Sq RSS AIC >> - as.numeric(do.grant) 1 0.71 6622.9 492.28 >> - as.factor(policy) 1 1.21 6623.4 492.29 >> - as.numeric(DMZ.dist) 1 1.91 6624.1 492.30 >> - as.numeric(city.grant) 1 5.07 6627.3 492.36 >> - as.numeric(nation.grant) 1 11.51 6633.7 492.47 >> - as.numeric(year) 1 29.58 6651.8 492.80 >> <none> 6622.2 494.27 >> - as.numeric(Seoul.dist) 1 673.22 7295.4 503.79 >> Step: AIC=492.28 >> pop.rate ~ as.numeric(year) + as.factor(policy) + as.numeric(nation.grant) + >> as.numeric(city.grant) + as.numeric(DMZ.dist) + as.numeric(Seoul.dist) >> Df Sum of Sq RSS AIC >> - as.factor(policy) 1 1.99 6624.9 490.32 >> - as.numeric(DMZ.dist) 1 2.09 6625.0 490.32 >> - as.numeric(city.grant) 1 7.18 6630.1 490.41 >> - as.numeric(nation.grant) 1 20.08 6643.0 490.64 >> - as.numeric(year) 1 28.89 6651.8 490.80 >> <none> 6622.9 492.28 >> - as.numeric(Seoul.dist) 1 697.46 7320.4 502.20 >> Step: AIC=490.32 >> pop.rate ~ as.numeric(year) + as.numeric(nation.grant) + >> as.numeric(city.grant) + >> as.numeric(DMZ.dist) + as.numeric(Seoul.dist) >> Df Sum of Sq RSS AIC >> - as.numeric(DMZ.dist) 1 2.08 6627.0 488.35 >> - as.numeric(city.grant) 1 10.65 6635.6 488.51 >> - as.numeric(nation.grant) 1 31.30 6656.2 488.88 >> - as.numeric(year) 1 31.44 6656.4 488.88 >> <none> 6624.9 490.32 >> - as.numeric(Seoul.dist) 1 732.88 7357.8 500.80 >> Step: AIC=488.35 >> pop.rate ~ as.numeric(year) + as.numeric(nation.grant) + >> as.numeric(city.grant) + >> as.numeric(Seoul.dist) >> Df Sum of Sq RSS AIC >> - as.numeric(city.grant) 1 9.86 6636.9 486.53 >> - as.numeric(year) 1 31.42 6658.4 486.92 >> - as.numeric(nation.grant) 1 33.33 6660.3 486.95 >> <none> 6627.0 488.35 >> - as.numeric(Seoul.dist) 1 754.40 7381.4 499.18 >> >> Error in step(lm(pop.rate ~ as.numeric(year) + as.factor(policy) + >> as.numeric(nation.grant) + : >> ------------------------------------------------------------------------------------------------------------------------------------------- >> number of rows in use has changed: remove missing values? >> ------------------------------------------------------------------------------------------ >> >> >> >> >> -- >> Kum-Hoe Hwang, Ph.D. >> >> Phone : 82-31-250-3516 >> Email : phdhw...@gmail.com >> > > -- > Peter Ehlers > University of Calgary -- Kum-Hoe Hwang, Ph.D. Phone : 82-31-250-3516 Email : phdhw...@gmail.com ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
