title: scikit learn svc coef0 parameter range
body: <p><a href="http://scikit-learn.org/stable/modules/generated/sklearn.svm.SVC.html#sklearn.svm.SVC" rel="noreferrer">Documentation here</a>. </p>
  
  <p>I'm wondering how important the <code>coef0</code> parameter is for SVCs under the polynomial and sigmoid kernels. As I understand it, it is the intercept term, just a constant as in linear regression to offset the function from zero. However to my knowledge, the SVM (scikit uses <a href="http://www.csie.ntu.edu.tw/~cjlin/libsvm/" rel="noreferrer">libsvm</a>) should find this value. </p>
  
  <p>What's a good general range to test over (is there one?). For example, generally with <code>C</code>, a safe choice is 10^-5 ... 10^5, going up in exponential steps. </p>
  
  <p>But for <code>coef0</code>, the value seems highly data dependent and I'm not sure how to automate choosing good ranges for each grid search on each dataset. Any pointers?</p>