liuliang01 0cf88d036f Add qid like ranklib format (#2749)
* add qid for https://github.com/dmlc/xgboost/issues/2748

* change names

* change spaces

* change qid to bst_uint type

* change qid type to size_t

* change qid first to SIZE_MAX

* change qid type from size_t to uint64_t

* update dmlc-core

* fix qids name error

* fix group_ptr_ error

* Style fix

* Add qid handling logic to SparsePage

* New MetaInfo format + backward compatibility fix

Old MetaInfo format (1.0) doesn't contain qid field. We still want to be able
to read from MetaInfo files saved in old format. Also, define a new format
(2.0) that contains the qid field. This way, we can distinguish files that
contain qid and those that do not.

* Update MetaInfo test

* Simply group assignment logic

* Explicitly set qid=nullptr in NativeDataIter

NativeDataIter's callback does not support qid field. Users of NativeDataIter
will need to call setGroup() function separately to set group information.

* Save qids_ in SaveBinary()

* Upgrade dmlc-core submodule

* Add a test for reading qid

* Add contributor

* Check the size of qids_

* Document qid format
2018-06-30 20:24:03 +00:00

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Markdown

# Get Started with XGBoost
This is a quick start tutorial showing snippets for you to quickly try out xgboost
on the demo dataset on a binary classification task.
## Links to Helpful Other Resources
- See [Installation Guide](../build.md) on how to install xgboost.
- See [Text Input Format](../input_format.md) on using text format for specifying training/testing data.
- See [How to pages](../how_to/index.md) on various tips on using xgboost.
- See [Tutorials](../tutorials/index.md) on tutorials on specific tasks.
- See [Learning to use XGBoost by Examples](../../demo) for more code examples.
## Python
```python
import xgboost as xgb
# read in data
dtrain = xgb.DMatrix('demo/data/agaricus.txt.train')
dtest = xgb.DMatrix('demo/data/agaricus.txt.test')
# specify parameters via map
param = {'max_depth':2, 'eta':1, 'silent':1, 'objective':'binary:logistic' }
num_round = 2
bst = xgb.train(param, dtrain, num_round)
# make prediction
preds = bst.predict(dtest)
```
## R
```r
# load data
data(agaricus.train, package='xgboost')
data(agaricus.test, package='xgboost')
train <- agaricus.train
test <- agaricus.test
# fit model
bst <- xgboost(data = train$data, label = train$label, max.depth = 2, eta = 1, nround = 2,
nthread = 2, objective = "binary:logistic")
# predict
pred <- predict(bst, test$data)
```
## Julia
```julia
using XGBoost
# read data
train_X, train_Y = readlibsvm("demo/data/agaricus.txt.train", (6513, 126))
test_X, test_Y = readlibsvm("demo/data/agaricus.txt.test", (1611, 126))
# fit model
num_round = 2
bst = xgboost(train_X, num_round, label=train_Y, eta=1, max_depth=2)
# predict
pred = predict(bst, test_X)
```
## Scala
```scala
import ml.dmlc.xgboost4j.scala.DMatrix
import ml.dmlc.xgboost4j.scala.XGBoost
object XGBoostScalaExample {
def main(args: Array[String]) {
// read trainining data, available at xgboost/demo/data
val trainData =
new DMatrix("/path/to/agaricus.txt.train")
// define parameters
val paramMap = List(
"eta" -> 0.1,
"max_depth" -> 2,
"objective" -> "binary:logistic").toMap
// number of iterations
val round = 2
// train the model
val model = XGBoost.train(trainData, paramMap, round)
// run prediction
val predTrain = model.predict(trainData)
// save model to the file.
model.saveModel("/local/path/to/model")
}
}
```