# [R] How to calculate vif of each term of model in R?

PIKAL Petr petr.pikal at precheza.cz
Thu Apr 23 15:45:03 CEST 2015

```Well. Your function results in error.

> f1<-function(model){
+ vfs<<-vif(model)
+ vfs
+ ex<<-subset(vfs,vfs>=10)
+ print(ex)
+ maxx<<-which.max(ex)
+ print(maxx)
+ mm<<-vector(mode = "numeric",length = 50)
+
+ mm<<-maxx
+ maxindex<<-which.max(ex)
+ print(maxindex)
+
+ }
> F1(model1)
Error: could not find function "F1"
>
> f1(model1)
>

Beside, why do you use global assignment.

<<-

within your function? I use R for more than 10 years and do not remember that I needed to use it.

You did not provide any data nor try to work on my suggestions. If you kept your mail copies to list you probably would get the answer more quickly.

You can use as.formula construction to programmatically select terms for update.

> fit

Call:
lm(formula = barviv ~ rutil + sio2 + teklat + fe, data = prov)

Coefficients:
(Intercept)        rutil         sio2       teklat           fe
1230.154        5.956       15.123       55.322     5571.923

> vif(fit)
rutil     sio2   teklat       fe
1.249975 1.702475 1.504633 1.094505
> which.max(vif(fit))
sio2
2
> wmvif <- which.max(vif(fit))
> update(fit, as.formula(paste(". ~ . -",names(vif(fit)[wmvif]))))

Call:
lm(formula = barviv ~ rutil + teklat + fe, data = prov)

Coefficients:
(Intercept)        rutil       teklat           fe
1220.25         6.04        97.44      5802.31

Cheers
Petr

> -----Original Message-----
> From: Methekar, Pushpa (GE Transportation, Non-GE)
> [mailto:pushpa.methekar at ge.com]
> Sent: Friday, April 17, 2015 2:47 PM
> To: PIKAL Petr
> Subject: RE: How to calculate vif of each term of model in R?
>
> Hey ,
> .........- names(vif(model1))[vmax])
> Is not working actually
> Update(model1,.~.-x8) is working fine.
>
>
>
> For that any option would you tell me.
> Update(model1,.~.-names(vif(model1))[vmax] means
>
> Update(model1,.~.-"x8")
> But it's not going to work.
>
> Look here is my program
>
> > require(rms)
> f1<-function(model){
> vfs<<-vif(model)
> vfs
> ex<<-subset(vfs,vfs>=10)
> print(ex)
> maxx<<-which.max(ex)
> print(maxx)
> mm<<-vector(mode = "numeric",length = 50)
>
> mm<<-maxx
> maxindex<<-which.max(ex)
> print(maxindex)
>
> }
> F1(model1)
>
>
>
> Output:
>    f1(model1)
>        x7        x8        x9
>  13.87063 220.96963 214.03413
> [1] 220.9696
> x8
>  2
>
>
> Now I have to do outside function explicitly
> model1<-update(model1,.~.-x8)
> then only I can remove my variable x8
>
> but I want to do in inside function so that automatically maximum
> element get eliminated .
>
>
> Thanks,
> Pushpa
>
>
>
> -----Original Message-----
> From: PIKAL Petr [mailto:petr.pikal at precheza.cz]
> Sent: Friday, April 17, 2015 5:25 PM
> To: Methekar, Pushpa (GE Transportation, Non-GE)
> Cc: r-help at r-project.org
> Subject: RE: How to calculate vif of each term of model in R?
>
> Hi
>
> > -----Original Message-----
> > From: Methekar, Pushpa (GE Transportation, Non-GE)
> > [mailto:pushpa.methekar at ge.com]
> > Sent: Friday, April 17, 2015 1:12 PM
> > To: PIKAL Petr
> > Subject: RE: How to calculate vif of each term of model in R?
> >
> > Hi Petr,
> > You got my problem ,the solution which u specified is little good but
> > with
> >
> >
> > >update(model1,.~. - names(vif(model1))[vmax])
> >
> >
> >
> > I won't be able to update my model .
> > Instead I have to write like
> >
> >
> > > update(model1,.~. - x8)
> >
>
> maybe something like
>
> fun = function(model1) {
>
> vmax <- which.max(vif(model1))
>
> while( vif(model1)[vmax]>=10) {
>
> model1 <- update(model1,.~. - names(vif(model1))[vmax])) vmax <-
> which.max(vif(model1))
>
> }
>
> return(model1)
>
> }
>
> I am not sure about cycle (i did not use while in R for a while).
>
> Without some data I cannot check syntax so it is up to you.
>
> Cheers
> Petr
>
>
> >
> > i.e my x which having highest vif value.
> > Each time for removing highest x .i  have to explicitly write ......-
> > x8) So is there any way to avoid this?
> >
> >
> >
> >
> > Thanks,
> > Pushpa
> >
> > -----Original Message-----
> > From: PIKAL Petr [mailto:petr.pikal at precheza.cz]
> > Sent: Friday, April 17, 2015 4:16 PM
> > To: Methekar, Pushpa (GE Transportation, Non-GE)
> > Subject: RE: How to calculate vif of each term of model in R?
> >
> > Comments to your first mail which are among lines and directly
> related
> >
> > I specifically mentioned it
> >
> >
> > If you have my first respond you can find them easier then now as
> they
> > are buried within your mail.
> >
> > Cheers
> > Petr
> >
> >
> > > -----Original Message-----
> > > From: Methekar, Pushpa (GE Transportation, Non-GE)
> > > [mailto:pushpa.methekar at ge.com]
> > > Sent: Friday, April 17, 2015 12:10 PM
> > > To: PIKAL Petr
> > > Subject: RE: How to calculate vif of each term of model in R?
> > >
> > >
> > > -----Original Message-----
> > > From: PIKAL Petr [mailto:petr.pikal at precheza.cz]
> > > Sent: Friday, April 17, 2015 3:38 PM
> > > To: Methekar, Pushpa (GE Transportation, Non-GE)
> > > Cc: r-help at r-project.org
> > > Subject: RE: How to calculate vif of each term of model in R?
> > >
> > >
> > > Cheers
> > > Petr
> > >
> > >
> > > > -----Original Message-----
> > > > From: Methekar, Pushpa (GE Transportation, Non-GE)
> > > > [mailto:pushpa.methekar at ge.com]
> > > > Sent: Friday, April 17, 2015 11:43 AM
> > > > To: PIKAL Petr
> > > > Subject: RE: How to calculate vif of each term of model in R?
> > > >
> > > > Car package
> > > >
> > > > -----Original Message-----
> > > > From: PIKAL Petr [mailto:petr.pikal at precheza.cz]
> > > > Sent: Friday, April 17, 2015 3:11 PM
> > > > To: Methekar, Pushpa (GE Transportation, Non-GE); r-help at r-
> > > project.org
> > > > Subject: RE: How to calculate vif of each term of model in R?
> > > >
> > > > Hi
> > > >
> > > > I did not see any answer so I try.
> > > >
> > > > Your question lacks some info:
> > > >
> > > > Which vif - car or HH?
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of
> > > > > Methekar, Pushpa (GE Transportation, Non-GE)
> > > > > Sent: Wednesday, April 08, 2015 10:24 AM
> > > > > To: r-help at r-project.org
> > > > > Subject: [R] How to calculate vif of each term of model in R?
> > > > >
> > > > >
> > > > > I am beginner in R doing modelling in R, I loaded excel sheet
> in
> > > > > R, i have chosen x elements and y elements then fitted model
> for
> > > linear
> > > > and
> > > > > second order regression. Now I have both models. I am bit
> > confused
> > > > how
> > > > > to calculate vif for each term in model like
> > > > >
> > > > > e.g model1<-lm(y1~x1+x2+.....x9) when I am using rms package
> > > > > then
> > > > it's
> > > > > giving me like
> > > > >
> > > > >     vif(model1)
> > > > >
> > > > >        x1         x2         x3         x4         x5
> x6
> > > > > x7
> > > > >
> > > > >  6.679692   1.520271   1.667125   3.618439   4.931810
> 2.073879
> > > > > 13.870630
> > > > >
> > > > >         x8         x9
> > > > >
> > > > >    220.969628 214.034135
> > > > >
> > > > > now i want to compare each term with std vif as vif>=10 and
> > > > > which
> > > > will
> > > > > satisfy this condition i want to delete that term and update
> > > model1.
> > > > i
> > > > > have done something like this
> > > > >
> > > > > fun = function(model1) {
> > > > >
> > > > >  for(i in 1:length(model1))    {
> > > > >
> > > > >       v=vif(model1)
> > > > >
> > > > >          ss=any(v[i]>=10)
> > > >
> > > > here you select only one item from vif, Why do you use any?
> > > >
> > > > >
> > > > >                 if(ss==1){update(model1,.~.,-v[i])}
> > > > >
> > > > >                 else{print("no update")}
> > > > >
> > > >
> > > > Why do you change i here?
> > > >
> > > > >                  i<-i+1
> > > > >
> > > > >     }
> > > > >
> > > > >
> > > > >
> > > > >         return(model1)
> > > > >
> > > > >       }
> > > > >
> > > >
> > > > if you want to get rid of all terms bigger than some threshold in
> > > once
> > > > you can use
> > > >
> > > > sel <- which(vif(model1)>10)
> > > >
> > > > and select values for update possibly by
> > > >
> > > > update(model1,.~. - names(vif(model1))[sel])
> > > >
> > > > or if you want to get rid one by one you can use
> > > >
> > > > vmax <- which.max(vif(model1))
> > > > and check if max vif value is bigger than 10.
> > > >
> > > > vif(model1)[vmax]>=10
> > > >
> > > > If it is just update with
> > > >
> > > > - names(vif(model1))[vmax])
> > > >
> > > > if it is not do not update.
> > > >
> > > > All of this untested.
> > > >
> > > > Cheers
> > > > Petr
> > > >
> > > > > fun(model1)
> > > > >
> > > > > but giving error as
> > > > >
> > > > > Error in if (ss == 1) { : missing value where TRUE/FALSE
> needed.
> > > > >
> > > > > please tell me how do i solve this problem.
> > > > >
> > > > >
> > > > >
> > > > >       [[alternative HTML version deleted]]
> > > > >
> > > > > ______________________________________________
> > > > > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more,
> > > > > see 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.
> > > >
> > >
>
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- a obsahuje-li nabídku, je adresát oprávněn nabídku bezodkladně přijmout; Odesílatel tohoto e-mailu (nabídky) vylučuje přijetí nabídky ze strany příjemce s dodatkem či odchylkou.
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This e-mail and any documents attached to it may be confidential and are intended only for its intended recipients.
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The sender of this e-mail shall not be liable for any possible damage caused by modifications of the e-mail or by delay with transfer of the email.

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```