I tried your suggestion on the toy example that was posted by David Carlson
a while back:
set.seed(42)
x <- 1:15
y <- x/(1+x) + rnorm(15,0,0.02)
I found that I had to:
(a) Wrap the "1/x" inside "I()".
(b) Set the offset term to be rep(1,length(x)).
Bottom line:
fit <- glm(y ~
0+I(1/
On 13-08-21 05:17 PM, Rolf Turner wrote:
>
>
> Thott about this a bit more and have now decided that I don't understand
> after all.
>
> Doesn't
>
> glm(1/y~x,family=gaussian(link="inverse"))
>
> fit the model
>
> 1/y ~ N(1/(a+bx), sigma^2)
>
> whereas what the OP wanted was
>
>
Rolf Turner xtra.co.nz> writes:
>
> On 21/08/13 11:23, Ye Lin wrote:
> > T
> > hanks for your insights Rolf! The model I want to fit is y=x/a+x with
> > no intercept, so I transformed it to 1/y=1+a/x as they are the same.
>
> For crying out loud, they are ***NOT*** the same. The equations y =
Rolf:
Thanks for this.
It nicely illustrates what to me is a fundamental problem: For many
scientists, it is not math ("stats") that is the stumbling block, but
rather the failure to understand how variability ("noise") affects the
experimental/observational process. One does tend to get more
phi
On 21/08/13 11:23, Ye Lin wrote:
> T
> hanks for your insights Rolf! The model I want to fit is y=x/a+x with
> no intercept, so I transformed it to 1/y=1+a/x as they are the same.
For crying out loud, they are ***NOT*** the same. The equations y =
x/(a+x) and
1/y = 1 + a/x are indeed algebraica
T
hanks for your insights Rolf! The model I want to fit is y=x/a+x with no
intercept, so I transformed it to 1/y=1+a/x as they are the same. but i
will look up nls() and see how to fit the model without transformation.
On Tue, Aug 20, 2013 at 2:45 PM, Rolf Turner wrote:
>
> (1) It is not accept
(1) It is not acceptable to use "wanna" in written English. You should say
"I want to fit a model ".
(2) The model you have fitted is *not* equivalent to the model you first
state.
If you write "y ~ x/(a+x)" you are tacitly implying that
y = x/(a+x) + E
where the "errors" E ar
TX 77840-4352
-Original Message-
From: r-help-boun...@r-project.org
[mailto:r-help-boun...@r-project.org] On Behalf Of Ye Lin
Sent: Tuesday, August 20, 2013 4:40 PM
To: R help
Subject: [R] how to code y~x/(x+a) in lm() function
Hey All,
I wanna to fit a model y~x/(a+x) to my data, here is the c
Hey All,
I wanna to fit a model y~x/(a+x) to my data, here is the code I use now:
lm((1/y-1)~I(1/x)+0, data=b)
and it will return the coefficient which is value of a
however, if I use the code above, I am not able to draw a curve the
presents this equation. How can I do this?
Thanks for your
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