I thank those who helped to solve a error in stepwise regression with
missing values.


Kum

*
*

A good solution that I have tried was Andreas's advice.

=====================================================================

Try

data<-na.omit(original database) before you run step() or stepAIC()

On Tue, Feb 16, 2010 at 8:09 PM, Peter Ehlers <ehlers@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 : phdhwang@gmail.com
>>
>>
> --
> Peter Ehlers
> University of Calgary
>



-- 
Kum-Hoe Hwang, Ph.D.

Phone : 82-31-250-3516
Email : phdhwang@gmail.com

	[[alternative HTML version deleted]]

