Ah, messages crossed.
A no-intercept model **assumes** the straight line fit must pass
through the origin. Unless there is a strong justification for such an
assumption, you should include an intercept.

-- Bert

On Sat, Aug 10, 2024 at 1:02 PM Bert Gunter <bgunter.4...@gmail.com> wrote:
>
> Is it because I failed to to add a column of ones for an intercept to
> the x matrix? TRhat would be my bad.
>
> -- Bert
>
>
> On Sat, Aug 10, 2024 at 12:59 PM Bert Gunter <bgunter.4...@gmail.com> wrote:
> >
> > Probably because you inadvertently ran different models. Without your code, 
> > I haven't a clue.
> >
> >
> > On Sat, Aug 10, 2024, 12:29 Yuan Chun Ding <ycd...@coh.org> wrote:
> >>
> >> HI Bert and Ben,
> >>
> >>
> >>
> >> Yes, running lm.fit using the matrix format is much faster. I read a 
> >> couple of online comments why it is faster.
> >>
> >>
> >>
> >> However, the residual values for three tested variables or genes from lm 
> >> function and lm.fit function are different, with Pearson correlation of 
> >> 0.55, 0.89, and 0.99.
> >>
> >>
> >>
> >> I have not found the reason.
> >>
> >>
> >>
> >> Thanks,
> >>
> >>
> >> Ding
> >>
> >>
> >>
> >> From: Bert Gunter <bgunter.4...@gmail.com>
> >> Sent: Friday, August 9, 2024 7:11 PM
> >> To: Ben Bolker <bbol...@gmail.com>
> >> Cc: Yuan Chun Ding <ycd...@coh.org>; r-help@r-project.org
> >> Subject: Re: [R] a fast way to do my job
> >>
> >>
> >>
> >> Better idea, Ben! It would work as you might expect it to to produce the 
> >> same results as the above: ##first make sure your regressor is a matrix: 
> >> pur2 <- matrix(purity2, ncol =1) ## convert the data frame variables into 
> >> a matrix dat <-
> >>
> >> Better idea, Ben!
> >>
> >>
> >>
> >> It would work as you might expect it to to produce the same results as
> >>
> >> the above:
> >>
> >>
> >>
> >> ##first make sure your regressor is a matrix:
> >>
> >> pur2 <- matrix(purity2, ncol =1)
> >>
> >> ## convert the data frame variables into a matrix
> >>
> >> dat <- as.matrix(gem751be.rpkm[ , 74:35164])
> >>
> >> ##then
> >>
> >> result <- residuals(lm.fit( x= pur2, y = dat))
> >>
> >>
> >>
> >> Cheers,
> >>
> >> Bert
> >>
> >>
> >>
> >> On Fri, Aug 9, 2024 at 6:38 PM Ben Bolker <bbol...@gmail.com> wrote:
> >>
> >> >
> >>
> >> > You can also fit a linear model with a matrix-valued response
> >>
> >> > variable, which should be even faster (not sure off the top of my head
> >>
> >> > how to get the residuals and reshape them to the dimensions you want)
> >>
> >> >
> >>
> >> > On Fri, Aug 9, 2024 at 9:31 PM Bert Gunter <bgunter.4...@gmail.com> 
> >> > wrote:
> >>
> >> > >
> >>
> >> > > See ?lm.fit.
> >>
> >> > > I must be missing something, because:
> >>
> >> > >
> >>
> >> > > results <- sapply(74:35164, \(i) residuals(lm.fit(purity2,
> >>
> >> > > gem751be.rpkm[, i] )))
> >>
> >> > >
> >>
> >> > > would give you a 751 x 35091 matrix of the residuals from each of the
> >>
> >> > > regressions.
> >>
> >> > > I assume it will be considerably faster than all the overhead you are
> >>
> >> > > carrying in your current code, but of course you'll have to try it and
> >>
> >> > > see. ... Assuming that I have interpreted your request correctly.
> >>
> >> > > Ignore if not.
> >>
> >> > >
> >>
> >> > > Cheers,
> >>
> >> > > Bert
> >>
> >> > >
> >>
> >> > > On Fri, Aug 9, 2024 at 4:50 PM Yuan Chun Ding via R-help
> >>
> >> > > <r-help@r-project.org> wrote:
> >>
> >> > > >
> >>
> >> > > > Dear R users,
> >>
> >> > > >
> >>
> >> > > > I am running the following code below,  the gem751be.rpkm is a 
> >> > > > dataframe with dim of 751 samples by 35164 variables,  73 phenotypic 
> >> > > > variables in the furst to 73rd column and 35091 genomic variables or 
> >> > > > genes in the 74th to 35164th columns.  What I need to do is to 
> >> > > > calculate the residuals for each gene using the simple linear 
> >> > > > regression model of genelist[i] ~ purity2;
> >>
> >> > > >
> >>
> >> > > > The following code is running,  it takes long time, but I have an 
> >> > > > expensive ThinkStation window computer.
> >>
> >> > > > Can you provide a fast way to do it?
> >>
> >> > > >
> >>
> >> > > > Thank you,
> >>
> >> > > >
> >>
> >> > > > Ding
> >>
> >> > > >
> >>
> >> > > > ---------------------------------------------------------------------------------
> >>
> >> > > >
> >>
> >> > > >
> >>
> >> > > > gem751be.rpkm <-merge(gem751be10, as.data.frame(t(rna849.fpkm2)),
> >>
> >> > > > +                           by.x="id2",by.y=0)
> >>
> >> > > > >   row.names(gem751be.rpkm)<-gem751be.rpkm$id3
> >>
> >> > > > >   
> >> > > > > colnames(gem751be.rpkm)<-gsub(colnames(gem751be.rpkm),pattern="-",replacement="_")
> >>
> >> > > > >   genelist <- gem751be.rpkm %>% dplyr::select(74:35164)
> >>
> >> > > > >   residuals <- NULL
> >>
> >> > > > >   for (i in 1:length(genelist)) {
> >>
> >> > > > +     #i=1
> >>
> >> > > > +     formula <- reformulate("purity2", response=names(genelist)[i])
> >>
> >> > > > +     model <- lm(formula, data = gem751be.rpkm)
> >>
> >> > > > +     resi <- as.data.frame(residuals(model))
> >>
> >> > > > +     colnames(resi)[1]<-names(genelist)[i]
> >>
> >> > > > +     resi <-as.data.frame(t(resi))
> >>
> >> > > > +     residuals <- rbind(residuals, resi)
> >>
> >> > > > +   }
> >>
> >> > > >
> >>
> >> > > >
> >>
> >> > > >
> >>
> >> > > > ----------------------------------------------------------------------
> >>
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> >>
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