xgboost 保存为pmml文件问题

xgboost 二进制文件，可以通过https://github.com/jpmml/jpmml-xgboost 保存为pmml文件，

但是feature map怎么生成呢

官方关于这点的说明，只有陈天奇的回复

https://github.com/dmlc/xgboost/issues/256

重点在这句

刚才那个开源转换工具在接受feature map的时候，是需要这样的文件的

0 cyl int

1 disp q

2 hp q

3 drat q

4 wt q

5 qsec q

6 vs=0 i

7 vs=1 i

8 am=0 i

9 am=1 i

10 gear int

11 carb int

有几点需要说明

1.分隔符必须是\t分割

2.int 代表int

3.q代表float

4.i代买 binary之后的int，

测试方法，可以通过以下代码获知

system('defaults write org.R-project.R force.LANG en_US.UTF-8')

install.packages("devtools")

library("devtools")

install_git("git://github.com/jpmml/r2pmml.git")

library("r2pmml")

library("xgboost")

data(mtcars)

# Convert selected columns from numeric datatype to integer or factor datatypes

mtcars$cyl = as.integer(mtcars$cyl)

mtcars$vs = as.factor(mtcars$vs)

mtcars$am = as.factor(mtcars$am)

mtcars$gear = as.integer(mtcars$gear)

mtcars$carb = as.integer(mtcars$carb)

mpg_y = mtcars[, 1]

mpg_X = mtcars[, 2:ncol(mtcars)]

# Generate feature map

mpg.fmap = r2pmml::genFMap(mpg_X)

r2pmml::writeFMap(mpg.fmap, "xgboost.fmap")

# Generate DMatrix

mpg.dmatrix = r2pmml::genDMatrix(mpg_y, mpg_X, "xgboost.svm")

set.seed(31)

# Train a linear regression model

mpg.xgb = xgboost(data = mpg.dmatrix, objective = "reg:linear", nrounds = 7)

# Save the model in XGBoost proprietary binary format

xgb.save(mpg.xgb, "xgboost.model")

# Dump the model in text format

xgb.dump(mpg.xgb, "xgboost.model.txt", fmap = "xgboost.fmap")