Validating¶

This example shows how to split a single dataset into two datasets, one used for training and the other used for testing.

Note that when splitting frames, H2O does not give an exact split. It’s designed to be efficient on big data using a probabilistic splitting method rather than an exact split. For example, when specifying a 0.75/0.25 split, H2O will produce a test/train split with an expected value of 0.75/0.25 rather than exactly 0.75/0.25. On small datasets, the sizes of the resulting splits will deviate from the expected value more than on big data, where they will be very close to exact.

r
python

library(h2o)
h2o.init()

# Import the prostate dataset
prostate.hex <- h2o.importFile(path = "http://h2o-public-test-data.s3.amazonaws.com/smalldata/prostate/prostate.csv", destination_frame = "prostate.hex")
print(dim(prostate.hex))
[1] 380   9

# Split dataset giving the training dataset 75% of the data
prostate.split <- h2o.splitFrame(data=prostate.hex, ratios=0.75)
print(dim(prostate.split[[1]]))
[1] 291   9
print(dim(prostate.split[[2]]))
[1] 89  9

# Create a training set from the 1st dataset in the split
prostate.train <- prostate.split[[1]]

# Create a testing set from the 2nd dataset in the split
prostate.test <- prostate.split[[2]]

# Generate a GLM model using the training dataset. x represesnts the predictor column, and y represents the target index.
prostate.glm <- h2o.glm(y = "CAPSULE",
                        x = c("AGE", "RACE", "PSA", "DCAPS"),
                        training_frame=prostate.train,
                        family="binomial",
                        nfolds=10,
                        alpha=0.5)

# Predict using the GLM model and the testing dataset
pred = h2o.predict(object=prostate.glm, newdata=prostate.test)

# View a summary of the prediction with a probability of TRUE
summary(pred$p1, exact_quantiles=TRUE)
p1
Min.   :0.1560
1st Qu.:0.2954
Median :0.3535
Mean   :0.4111
3rd Qu.:0.4369
Max.   :0.9989