Mimic数据提取：Exception while reading from stream

导入数据：’utf-8′ codec can’t decode byte 0xa1 in position 10971: invalid start byte

Error in eval(family$initialize) : y值必需满足0 <= y <= 1

Error in gbm.unify(model, data):Models built on data with categorical features are not supported – please encode them before training.

在回归分析中，如何修改分类变量的参照/参考/ref因子