R help - Sep 2016 - Using lm's subset parameter results in Error in xj[i] : invalid subscript type 'list'

I'm trying to take lm on a subset of my dataset and to do this I believe 
I need to pass my subset of the data as the subset parameter of lm.

So I do my subsetting:

firstkids <- kidmomhsage[0:234,], i.e. the first 234 rows of the data 
frame.

Then construct the model:

fit4 <- lm(kidmomhsage$kid_score ~ kidmomhsage$mom_age + 
kidmomhsage$mom_hs + kidmomhsage$mom_age * kidmomhsage$mom_hs, 
subset=firstkids)

which results in:

Error in xj[i] : invalid subscript type 'list'

I read somewhere a recommendation to use "unlist":

fit4 <- lm(kidmomhsage$kid_score ~ kidmomhsage$mom_age + 
kidmomhsage$mom_hs + kidmomhsage$mom_age * kidmomhsage$mom_hs, 
subset=unlist(firstkids))

which seems to not produce the error and results in some sort of model, 
but is this model the correct one (i.e. for the data set firstkids, just 
as it originally appears)? How does unlist change the data?

By subsetting the rows in the firstkids data frame, you've already
subsetted your data.

Try specifying firstkids as your data instead of a subset in the lm call.
Also, eliminate the kidmomhsage prefix from all of your variables since
you're running the linear model on a different data frame(firstkids)

Something along this line:

lm(kid_score ~ mom_age ...., data = firstkids)

*Jorge Cimentada*
*Ph.D. Candidate*
Dpt. Ci?ncies Pol?tiques i Socials
Ramon Trias Fargas, 25-27 | 08005 Barcelona

Office 24.331
[Tel.] 697 382 009
jorge.cimentada at upf.edu
http://www.upf.edu/dcpis/



On Tue, Sep 20, 2016 at 10:00 AM, mviljamaa <mviljamaa at kapsi.fi> wrote:
> I'm trying to take lm on a subset of my dataset and to do this I
believe I
> need to pass my subset of the data as the subset parameter of lm.
>
> So I do my subsetting:
>
> firstkids <- kidmomhsage[0:234,], i.e. the first 234 rows of the data
> frame.
>
> Then construct the model:
>
> fit4 <- lm(kidmomhsage$kid_score ~ kidmomhsage$mom_age +
> kidmomhsage$mom_hs + kidmomhsage$mom_age * kidmomhsage$mom_hs,
> subset=firstkids)
>
> which results in:
>
> Error in xj[i] : invalid subscript type 'list'
>
> I read somewhere a recommendation to use "unlist":
>
> fit4 <- lm(kidmomhsage$kid_score ~ kidmomhsage$mom_age +
> kidmomhsage$mom_hs + kidmomhsage$mom_age * kidmomhsage$mom_hs,
> subset=unlist(firstkids))
>
> which seems to not produce the error and results in some sort of model,
> but is this model the correct one (i.e. for the data set firstkids, just as
> it originally appears)? How does unlist change the data?
>
> ______________________________________________
> 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/posti
> ng-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
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Hi

see in line
> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of
mviljamaa
> Sent: Tuesday, September 20, 2016 10:01 AM
> To: r-help at r-project.org
> Subject: [R] Using lm's subset parameter results in Error in xj[i] :
invalid
> subscript type 'list'
>
> I'm trying to take lm on a subset of my dataset and to do this I
believe I need
> to pass my subset of the data as the subset parameter of lm.
>
> So I do my subsetting:
>
> firstkids <- kidmomhsage[0:234,], i.e. the first 234 rows of the data
frame.
It works, however line numbering in R starts with 1 not 0. R is clever enough to
subset with 0:xx vector however you will not get line 1 by subsetting with 0

dd<-data.frame(a=1:10, b=rnorm(10))
dd[0,]
[1] a b
<0 rows> (or 0-length row.names)
>
> Then construct the model:
>
> fit4 <- lm(kidmomhsage$kid_score ~ kidmomhsage$mom_age +
> kidmomhsage$mom_hs + kidmomhsage$mom_age *
> kidmomhsage$mom_hs,
> subset=firstkids)
You definitelly should spend some time with introductory documentation. The
above construction shall be e.g.

fit4 <- lm(kid_score ~ mom_age +mom_hs + mom_age *mom_hs, data = kidmomhsage,
subset=1:234)
>
> which results in:
>
> Error in xj[i] : invalid subscript type 'list'
>
> I read somewhere a recommendation to use "unlist":
I wonder where did you read such recommendation for lm function, you should
better avoid that source.

Cheers
Petr
>
> fit4 <- lm(kidmomhsage$kid_score ~ kidmomhsage$mom_age +
> kidmomhsage$mom_hs + kidmomhsage$mom_age *
> kidmomhsage$mom_hs,
> subset=unlist(firstkids))
>
> which seems to not produce the error and results in some sort of model, but
> is this model the correct one (i.e. for the data set firstkids, just as it
originally
> appears)? How does unlist change the data?
>
> ______________________________________________
> 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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