为什么在bp神经网络训练中总是出现如下错误，第一次时运算很成功，可是后面每次都这样，是怎么回事，求大神解答
??? Insufficient number of outputs from right hand
side of equal sign to satisfy assignment.

Error in ==> nntool at 694
      [errmsg,errid] = me.message;

com.mathworks.jmi.MatlabException: Insufficient number of outputs from right hand side of equal sign to satisfy assignment.