# [R-meta] converting escalc ROM outputs to the log-2 scale

Divya Ravichandar d|vy@ @end|ng |rom @econdgenome@com
Sat Dec 12 01:09:56 CET 2020

```Hi Dr. Wolfgang

Thank you for getting back to me. Could you help me understand more on why
we square the log(2) in the vi calculation?

On Fri, Dec 11, 2020 at 6:37 PM Viechtbauer, Wolfgang (SP) <
wolfgang.viechtbauer using maastrichtuniversity.nl> wrote:

> Dear Divya,
>
> If y_i ~ N(theta_i, v_i), then for any constant c, c*y_i ~ N(c*theta_i,
> c^2 * v_i).
>
> So, it would be yi_new = yi/log(2) and vi_new = vi/log(2)^2.
>
> Best,
> Wolfgang
>
> >-----Original Message-----
> >From: R-sig-meta-analysis [mailto:
> r-sig-meta-analysis-bounces using r-project.org]
> >On Behalf Of Divya Ravichandar
> >Sent: Friday, 11 December, 2020 23:36
> >To: r-sig-meta-analysis using r-project.org
> >Subject: [R-meta] converting escalc ROM outputs to the log-2 scale
> >
> >Hi all
> >
> >I have a question around changing the scale of *yi *and *vi *exported
> >from *escalc()
> >*function when using *measure=ROM.* Based on the documentation, this
> >function exports *yi *in natural log (ln) scale. --> yi =
> >ln(grp1-mean/grp2-mean) and then the associated vi.
> >
> >I am interested in obtaining the *log-2 fold change. *Is there a way to
> >convert yi & vi from *escalc(measure = ROM,...) *to this scale. Would it
> be
> >reasonable to simply transform the values by converting from log-e ->
> log-2
> >scale by
> >yi_new = yi/log(2) and vi_new = vi/log(2)
> >
> >Thank you
> >
> >--
> >*Divya Ravichandar*
> >Scientist
> >Second Genome
>

--
*Divya Ravichandar*
Scientist
Second Genome

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