随机森林出现error： New factor levels not present in the training data-经管之家官网！

我要用随机森林回归，预测负荷。程序如下，
ntdata1<-read.csv('C:/Users/*****ingting/Desktop/ntdata1.csv',header=TRUE)
ntdata2<-read.csv('C:/Users/*****ingting/Desktop/ntdata2.csv',header=TRUE)
library(randomForest)
ranfor<-randomForest(Load~.,data=ntdata1,ntree=1000,mtry=2,importance=TRUE)
print(ranfor)
pred<-predict(ranfor,ntdata2)
print(pred)
ntdata1,即训练样本表头是http://file:///C:\\Users\\*****ingting\\Documents\\Tencent Files\\995404160\\Image\\C2C\\M2UA(@DZCTL{YNF8AMXSLCQ.pnghttp://file:///C:\\Users\\*****ingting\\Documents\\Tencent Files\\995404160\\Image\\C2C\\M2UA(@DZCTL{YNF8AMXSLCQ.png

Time Stamp	Name	Load	Max Temp	Min Temp	Max Wet Bulb	Min Wet Bulb
1	NORTH	784.157785	11	-7	9	-7
2	NORTH	840.695986	-7	-14	-7	-14
3	NORTH	847.355451	-4	-16	-5	-16
4	NORTH	807.756122	19	-17	16	-17
5	NORTH	753.443189	31	17	30	15

ntdata2,也即测试样本表头是

Time Stamp	Name	Load	Max Temp	Min Temp	Max Wet Bulb	Min Wet Bulb
1	North	751.8797945	37	16	35	15
2	North	739.916667	37	27	34	25
3	North	754.0072414	27	10	24	9
4	North	767.0924658	27	8	22	7

。但是运行程序后出现
> pred<-predict(ranfor,ntdata2)Error in predict.randomForest(ranfor, ntdata2) :
New factor levels not present in the training data
求大神指导，我到底哪个地方错了。