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can anyone help me with how to calculate R-squared for a logistic regression- How do I use the deviance for this Purpose ?

Additionaly, the question in matlab: I am calculating a psychometric function using the "glmfit" function in matlab, with 'probit' parameter.

It returns "dev" variable, and I do not understand how to calculate from this value the goodness of fit of the model - R-squared.

Any advice?

Alexis
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Orit Nizri
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    I think only pseudo exists – SmallChess Mar 11 '17 at 22:07
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    Welcome to CV. Since you're new here, you may want to take our [tour], which has information for new users. There is no direct equivalent of $R^2$ (in the linear regression) for logistic regression. But it is possible to compute other measures resembling $R^2$ called pseudo-$R^2$'s. However, their interpretation might be tricky and yield different results. For more information, check this [link](http://tinyurl.com/hp2o2ub). Also, questions focusing on *programming, debugging, or performing routine operations within a statistical computing platform* are off-topic here. – T.E.G. Mar 11 '17 at 22:07
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    While questions focusing on *programming, debugging, or performing routine operations within a statistical computing platform* are off-topic here, they on-topic with the sister site [so]. [so] has the expectation that you will provide what code you have created and explain where you are stuck. – Tavrock Mar 11 '17 at 22:35
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    @StudentT There's also Lonnie Magee's Generalized $R^{2}$ based on log-likelihood measures: Magee, L. (1990). [$R^{2}$ measures based on Wald and likelihood ratio joint significance tests](http://www.tandfonline.com/doi/abs/10.1080/00031305.1990.10475731). *The American Statistician*, 44(3):250–253. – Alexis Mar 12 '17 at 00:52

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