Hi,
2008/8/21 Mario Maiworm <[EMAIL PROTECTED]>
> Hi,
> I want to fit some psychophysical data with cumulative gaussians. There is
> quite a convenient toolbox for matlab called 'psignifit' (formerly known as
> 'psychofit'). It allows the lower bound of the sigmoid to vary slightly
> from
> zero,
__
>>> -Original Message-
>>> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
>>> project.org] On Behalf Of Paul Artes
>>> Sent: Thursday, August 21, 2008 5:37 PM
>>> To: r-help@r-project.org
>>> Subject: Re: [R] psychometric f
On 08/21/08 17:48, Mario Maiworm wrote:
> >>> Two comments. First, it isn't clear to me why you want the upper
> >>> bound to differ from 1. Apparently you have some theoretical reason
> >>> for using a cumulative gaussian. Wouldn't the same theory tell you
> >>> that the upper bound should be 1
>>> Two comments. First, it isn't clear to me why you want the upper
>>> bound to differ from 1. Apparently you have some theoretical reason
>>> for using a cumulative gaussian. Wouldn't the same theory tell you
>>> that the upper bound should be 1?
the reason why I use cumulative gaussians is
There is a nice paper by Yssaad-Fesselier and Knoblauch on "Modelling
Psychometric Functions in R".
http://hal.archives-ouvertes.fr/docs/00/13/17/99/PDF/B125.pdf
You might also be interested in this:
http://www.journalofvision.org/5/5/8/article.aspx
which comes from the same group as the psignifi
Hi Mario,
in many applications there is not much difference between logistic and Gaussian
distributions (just as logit and probit models often produce similar fits)...
Moreover it's possible to fit sigmoidal curves using models such as the
(log-)logistic
where the lower and/upper limits are esti
> > >>> > -Original Message-
> > >>> > From: [EMAIL PROTECTED]
> > >>> > [mailto:[EMAIL PROTECTED] On Behalf Of Mario Maiworm
> > >>> > Sent: Thursday, August 21, 2008 7:05 AM
> > >>> > To:
uses optim()
> -Original Message-
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of Mario Maiworm
> Sent: Thursday, August 21, 2008 9:16 AM
> To: r-help@r-project.org
> Subject: Re: [R] psychometric functions
>
> Thank you harold. Hmm thats bad news
l Message-
>>> From: Doran, Harold [mailto:[EMAIL PROTECTED]
>>> Sent: Thursday, August 21, 2008 2:40 PM
>>> To: Mario Maiworm; r-help@r-project.org
>>> Subject: RE: [R] psychometric functions
>>>
>>> I am pretty certain a function for this model doe
in the ltm package.
-Original Message-
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Mario Maiworm
Sent: Thursday, August 21, 2008 7:05 AM
To: r-help@r-project.org
Subject: [R] psychometric functions
Hi,
I want to fit some psychophysical data with cumulative
gaussians. Th
nds to 1) and this is in the ltm package.
> -Original Message-
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of Mario Maiworm
> Sent: Thursday, August 21, 2008 7:05 AM
> To: r-help@r-project.org
> Subject: [R] psychometric functions
>
&g
Hi,
I want to fit some psychophysical data with cumulative gaussians. There is
quite a convenient toolbox for matlab called 'psignifit' (formerly known as
'psychofit'). It allows the lower bound of the sigmoid to vary slightly from
zero, aswell as the upper bound to vary from one. with these two fr
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