我将一些属性变量选入Factors列表，对因变量做多项Logistic回归分析时，数据矩阵出现奇异的情况，如下显示：

Warnings
Unexpected singularities in the Hessian matrix are encountered. This indicates that either some predictor variables should be excluded or some categories should be merged.
The NOMREG procedure continues despite the above warning(s). Subsequent results shown are based on the last iteration. Validity of the model fit is uncertain.

我该如何处理啊？