Hi, i'm trying to do the House Price Prediction (dataset from Kaggle), i want to use the lasso régression and the redige régression. But the probleme is that after using model.matrix, the number of columns reduced. I've already checked my dataset, i don't have any NA value. So is there any other raison that this situation happen? Can some one please help me to resolve this probleme, thank you a lot !

Here it the link of this dataset : House Prices - Advanced Regression Techniques | Kaggle

Here is what i do to the train dataset and the same thing to the test dataset ： I only use the numeric variables and removed the ones with a lot of NA values. I just want to practice lasso and ridge régression.

Then, here is what i do to transform my data frame to matrix.

```
train_x <- model.matrix(SalePrice~., data = PBdata[, -SalePrice])
train_y <- PBdata$SalePrice
```

```
dim(PBdata)
dim(train_x)
```

[1] 1259 34 [1] 1259 30