title: Error zero variance for at least one class in Variables
body: <p>Sorry for the newbie question I am new to R and couldn't find the answer anywhere.
  I am using the caret package.
  I have a data of 3000 Observation sampled from a bigger data set.
  I am trying to train the NB classifier on this data using the following code.</p>
  
  <pre><code>model_nb_2002= train(trainingdata_2002$CLA_2.CANCELER ~., data=trainingdata_2002, method="nb",trControl=fitCtrl, metric="Accuracy")
  </code></pre>
  
  <p>but always get the error message.</p>
  
  <blockquote>
    <p>In eval(expr, envir, enclos) :   model fit failed for Fold10.Rep05:
    usekernel=FALSE, fL=0 Error in NaiveBayes.default(x, y, usekernel =
    param$usekernel, fL = param$fL,  :    Zero variances for at least one
    class in variables: NUM_0.HH_IM_HAUS10, NUM_0.HH_IM_HAUS12,
    NUM_0.HH_IM_HAUS13, NUM_0.HH_IM_HAUS137, NUM_0.HH_IM_HAUS14,
    NUM_0.HH_IM_HAUS15, NUM_0.HH_IM_HAUS16, NUM_0.HH_IM_HAUS17,
    NUM_0.HH_IM_HAUS18, NUM_0.HH_IM_HAUS19, NUM_0.HH_IM_HAUS20,
    NUM_0.HH_IM_HAUS21, NUM_0.HH_IM_HAUS22, NUM_0.HH_IM_HAUS23,
    NUM_0.HH_IM_HAUS24, NUM_0.HH_IM_HAUS25, NUM_0.HH_IM_HAUS26,
    NUM_0.HH_IM_HAUS27, NUM_0.HH_IM_HAUS28, NUM_0.HH_IM_HAUS29,
    NUM_0.HH_IM_HAUS30, NUM_0.HH_IM_HAUS31, NUM_0.HH_IM_HAUS32,
    NUM_0.HH_IM_HAUS33, NUM_0.HH_IM_HAUS34, NUM_0.HH_IM_HAUS35,
    NUM_0.HH_IM_HAUS36, NUM_0.HH_IM_HAUS37, NUM_0.HH_IM_HAUS38,
    NUM_0.HH_IM_HAUS39, NUM_0.HH_IM_HAUS40, NUM_0.HH_IM_HAUS41,
    NUM_0.HH_IM_HAUS42, NUM_0.HH_IM_HAUS43, NUM_0.HH_IM_HAUS44,
    NUM_0.HH_IM_HAUS45, NUM_0.HH_IM_HAUS46, NUM_0.HH_IM_HAUS47,
    NUM_0.HH_IM_HAUS49, NUM_0.HH_IM_HAUS52, NUM_0. [... truncated]</p>
  </blockquote>
  
  <p>I have no idea which attribute is causing this problem. If I understand it right there is an attribute causing this Problem because it misses the variance needed for the prediction.
  Any help would be appreciated.</p>