Aloha all,
Well if all youʻre doing is plotting data, then sure, you can have a change
of axes and something in g will still be in g with log-transformed axes.
But does this apply to fitting models of BM or OU? The model is assuming
that the "errors" or the small jumps in phenotype comes from a
Marguerite asked:
> First - Joe - what do you mean by log(grams) has no units? The units of grams
> is a unit, so log(mass) will have units of log-gm. As log is not the same as
> 1/gm, log(gm) cannot be unit-free.
I looked it up on Wikipedia, and was assured by it that Marguerite is
right,
logy, UT Knoxville
President-Elect, Society of Systematic Biologists
He/Him/His
From: R-sig-phylo on behalf of Karla Shikev
Date: Friday, March 19, 2021 at 2:12 PM
To: R Sig Phylo Listserv
Subject: [R-sig-phylo] units of sigsq
Dear all,
Please indulge me in a simple (newbie) question.
I
Aloha all,
Iʻm still reeling from the Atlanta murders and the rise of hate in general,
so I may not be thinking straight, but if weʻre talking about Brownian
motion, Iʻm not sure this is quite right.
If the trait is log(grams) then the trait is unit-free.
>
First - Joe - what do you mean by
Ted Garland asked:
OK, Joe, that's for one trait at a time.
> Would you please continue your discourse, but extend to multiple traits
> and their covariances
>
OK, assuming that’s not a joke which it seems it was. If all characters
are log of something, their variances all have units of sites
OK, Joe, that's for one trait at a time.
Would you please continue your discourse, but extend to multiple traits and
their covariances?
Many thanks,
Ted
P.S - What's the emoji for tongue in cheek? I don't see a great one, but
here's an emoticon:
:-J
On Fri, Mar 19, 2021 at 1:08 PM Joe
Folks --
If the trait is log(grams) then the trait is unit-free. The "time"
is probably branch length from a phylogeny. That in turn (from DNA
data) is usually DNA substitutions per site.
So the units of the standard deviation aresites per substitution.
But this is not the standard
Great! thanks, Florian!
On Fri, Mar 19, 2021 at 4:45 PM Florian Boucher
wrote:
> Hi Karla,
>
> you're almost right, but since sigsq is the variance of the random walk
> per unit time its unit is actually [unit of the trait]^2/[unit of time]
>
> Cheers,
> Florian
>
> Le ven. 19 mars 2021 à
Hi Karla,
you're almost right, but since sigsq is the variance of the random walk per
unit time its unit is actually [unit of the trait]^2/[unit of time]
Cheers,
Florian
Le ven. 19 mars 2021 à 19:12, Karla Shikev a écrit :
> Dear all,
>
> Please indulge me in a simple (newbie) question.
>
>
Dear all,
Please indulge me in a simple (newbie) question.
If I have a continuous trait (log(body size in g)) and a calibrated tree
and use fitContinuous to estimate sigsq using a BM model, what is the unit
of the siqsq estimate? log(g)/My?
Thanks for your patience,
Karla
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