Anomaly Detection With Deep Learning in R With H2O [Code Snippet]

The following R script downloads an ECG dataset (training and validation) from the internet and performs deep learning-based anomaly detection on it.

library(h2o)
h2o.init()
# Import ECG train and test data into the H2O cluster
train_ecg <- h2o.importFile(
 path = "http://h2o-public-test-data.s3.amazonaws.com/smalldata/anomaly/ecg_discord_train.csv", 
 header = FALSE, 
 sep = ",")
test_ecg <- h2o.importFile(
 path = "http://h2o-public-test-data.s3.amazonaws.com/smalldata/anomaly/ecg_discord_test.csv", 
 header = FALSE, 
 sep = ",")

# Train deep autoencoder learning model on "normal" 
# training data, y ignored 
anomaly_model <- h2o.deeplearning(
 x = names(train_ecg), 
 training_frame = train_ecg, 
 activation = "Tanh", 
 autoencoder = TRUE, 
 hidden = c(50,20,50), 
 sparse = TRUE,
 l1 = 1e-4, 
 epochs = 100)

# Compute reconstruction error with the Anomaly 
# detection app (MSE between output and input layers)
recon_error <- h2o.anomaly(anomaly_model, test_ecg)

# Pull reconstruction error data into R and 
# plot to find outliers (last 3 heartbeats)
recon_error <- as.data.frame(recon_error)
recon_error
plot.ts(recon_error)

# Note: Testing = Reconstructing the test dataset
test_recon <- h2o.predict(anomaly_model, test_ecg) 
head(test_recon)

h2o.saveModel(anomaly_model, "/Users/avkashchauhan/learn/tmp/anomaly_model.bin")
h2o.download_pojo(anomaly_model, "/Users/avkashchauhan/learn/tmp/", get_jar = TRUE)

h2o.shutdown(prompt= FALSE)

 That's it — enjoy!