Re: [Scikit-learn-general] SVC and unbalanced dataset

2014-09-12 Thread ZORAIDA HIDALGO SANCHEZ
Thanks for all the suggestions. I will try them and let you know. El 10/09/14 16:46, "Andy" escribió: >On 09/10/2014 09:07 AM, Gael Varoquaux wrote: >> How are you measuring your errors? If you are using the zero-one loss >> (accuracy score), you are taking in account only the binary decisions,

Re: [Scikit-learn-general] SVC and unbalanced dataset

2014-09-10 Thread Andy
On 09/10/2014 09:07 AM, Gael Varoquaux wrote: > How are you measuring your errors? If you are using the zero-one loss > (accuracy score), you are taking in account only the binary decisions, > and not a possible decision function. I have found that in the situation > of unbalanced classes, it could

Re: [Scikit-learn-general] SVC and unbalanced dataset

2014-09-10 Thread Gael Varoquaux
How are you measuring your errors? If you are using the zero-one loss (accuracy score), you are taking in account only the binary decisions, and not a possible decision function. I have found that in the situation of unbalanced classes, it could be useful to threshold the decision function at a dif

Re: [Scikit-learn-general] SVC and unbalanced dataset

2014-09-10 Thread Eustache DIEMERT
ustache DIEMERT >> Responder a: "scikit-learn-general@lists.sourceforge.net" < >> scikit-learn-general@lists.sourceforge.net> >> Fecha: martes, 9 de septiembre de 2014 16:33 >> Para: "scikit-learn-general@lists.sourceforge.net" < >> scikit-learn-gene

Re: [Scikit-learn-general] SVC and unbalanced dataset

2014-09-09 Thread Albert Thomas
tiembre de 2014 16:33 > Para: "scikit-learn-general@lists.sourceforge.net" < > scikit-learn-general@lists.sourceforge.net> > Asunto: Re: [Scikit-learn-general] SVC and unbalanced dataset > > besides class weights you may try to downsample your negativ

Re: [Scikit-learn-general] SVC and unbalanced dataset

2014-09-09 Thread ZORAIDA HIDALGO SANCHEZ
@lists.sourceforge.net>> Fecha: martes, 9 de septiembre de 2014 16:33 Para: "scikit-learn-general@lists.sourceforge.net<mailto:scikit-learn-general@lists.sourceforge.net>" mailto:scikit-learn-general@lists.sourceforge.net>> Asunto: Re: [Scikit-learn-general] SVC and

Re: [Scikit-learn-general] SVC and unbalanced dataset

2014-09-09 Thread Eustache DIEMERT
besides class weights you may try to downsample your negative examples. E/ 2014-09-09 14:32 GMT+02:00 ZORAIDA HIDALGO SANCHEZ < zoraida.hidalgosanc...@telefonica.com>: > Dear all, > > I am trying to classify a dataset with a binary target. Number of positive > instances represents only the 3% of

Re: [Scikit-learn-general] SVC and unbalanced dataset

2014-09-09 Thread ZORAIDA HIDALGO SANCHEZ
Dear all, I am trying to classify a dataset with a binary target. Number of positive instances represents only the 3% of the total instances. I have tried using SVC with neither auto_weight nor sample_weight and the confusion matrix shows that all instances are classified as negative. However, if