Re: Reverse of Fisher's r to z
Yes, there are reasons for using the transformation frm z to r. And, there are published tables of this. For example, Appendix Table B.19 of Zar, Biostatistical Analysis, 4th ed., 1999. Jerrold H. Zar, Professor Department of Biological Sciences Northern Illinois University DeKalb, IL 60115 [EMAIL PROTECTED] === >>> Will Hopkins <[EMAIL PROTECTED]> 04/09/01 04:29AM >>> It's elementary algebra, Cherilyn. BTW, it's z = 0.5log..., not sqrt. So r = (e^2z - 1)/(e^2z + 1). Will = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: Reverse of Fisher's r to z
Thanks-- my algebra (and apparently my eyesight too) has gotten a bit creepy around the edges, so I didn't trust it for something this important Truly appreciate it!!! Best, Cherilyn On Mon, 9 Apr 2001, Will Hopkins wrote: > It's elementary algebra, Cherilyn. BTW, it's z = 0.5log..., not sqrt. > > So r = (e^2z - 1)/(e^2z + 1). > > Will > > = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: Reverse of Fisher's r to z
Cherilyn Young wrote:
> I have an itchy little question about the familiar Fisher's r to z
> transformation: The formula, expressed as z= sqrt (log e ( (1+r)/(1-r))),
> is in pretty much any older stats textbook. Does anyone know of a source
> where the equation is written to solve for r? I know it's a very uncommon
> use (if used at all in this way ), but I've got a very legitimate research
> need (and my brain's doing odd things when I'm trying to rewrite the
> equation).
r.back <- function(x)
{
((2.71828182845905^(2 * x)) - 1)/((2.71828182845905^(2 * x)) + 1)
}
fish.z <- function(x)
{
ifelse(x == 0, 0, 0.5 * log((1 + abs(x))/(1 - abs(x))) * (x/abs(x)))
}
Examples:
> fish.z(.45)
[1] 0.4847003
> r.back(.4847003)
[1] 0.45
> r.back(fish.z(.45))
[1] 0.45
HTH,
Chuck
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Chuck Cleland
Institute for the Study of Child Development
UMDNJ--Robert Wood Johnson Medical School
97 Paterson Street
New Brunswick, NJ 08903
phone: (732) 235-7699
fax: (732) 235-6189
http://www2.umdnj.edu/iscdweb/
http://members.nbci.com/cmcleland/
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Instructions for joining and leaving this list and remarks about
the problem of INAPPROPRIATE MESSAGES are available at
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Re: Reverse of Fisher's r to z
It's elementary algebra, Cherilyn. BTW, it's z = 0.5log..., not sqrt. So r = (e^2z - 1)/(e^2z + 1). Will = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Reverse of Fisher's r to z
Hi everyone, I have an itchy little question about the familiar Fisher's r to z transformation: The formula, expressed as z= sqrt (log e ( (1+r)/(1-r))), is in pretty much any older stats textbook. Does anyone know of a source where the equation is written to solve for r? I know it's a very uncommon use (if used at all in this way ), but I've got a very legitimate research need (and my brain's doing odd things when I'm trying to rewrite the equation). Thanks in advance, Cherilyn = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
