Changing the Column Type¶

H2O algorithms will treat a problem as a classification problem if the column type is factor and a regression problem if the column type is numeric. You can force H2O to use either classification or regression by changing the column type.

library(h2o)
h2o.init()

# Import the cars dataset:
cars_df <- h2o.importFile("https://s3.amazonaws.com/h2o-public-test-data/smalldata/junit/cars_20mpg.csv")

# Check the column type for the "cylinders" column:
print(h2o.isnumeric(cars_df["cylinders"]))
#TRUE

# Change the column type to a factor:
cars_df["cylinders"] <- as.factor(cars_df["cylinders"])

# Verify that the column is now a factor:
print(h2o.isfactor(cars_df["cylinders"]))
#TRUE

# Change the column type back to numeric:
cars_df["cylinders"] <- as.numeric(cars_df["cylinders"])
# Verify that the column is now numeric and not a factor:
print(h2o.isfactor(cars_df["cylinders"]))
#FALSE
print(h2o.isnumeric(cars_df["cylinders"]))
#TRUE

# Change multiple columns to factors:
cars_df[c("cylinders","economy_20mpg")] <- as.factor(cars_df[c("cylinders","economy_20mpg")])

# Verify that the columns are now factors:
print(h2o.isfactor(cars_df[c("cylinders","economy_20mpg")]))
# TRUE TRUE

import h2o
h2o.init()

# Import the cars dataset:
cars_df = h2o.import_file("https://s3.amazonaws.com/h2o-public-test-data/smalldata/junit/cars_20mpg.csv")

# Check the column type for the 'cylinders' column:
print(cars_df['cylinders'].isnumeric())
#[True]

# Change the column type to a factor:
cars_df['cylinders'] = cars_df['cylinders'].asfactor()

# Verify that the column is now a factor:
print(cars_df['cylinders'].isfactor())
#[True]

# Change the column type back to numeric:
cars_df["cylinders"] = cars_df["cylinders"].asnumeric()
# Verify that the column is now numeric and not a factor:
print(cars_df['cylinders'].isfactor())
#[False]
print(cars_df['cylinders'].isnumeric())
#[True]

# Reload data:
cars_df = h2o.import_file("https://s3.amazonaws.com/h2o-public-test-data/smalldata/junit/cars_20mpg.csv")

# Change multiple columns to factors:
cars_df[['cylinders','economy_20mpg']] = cars_df[['cylinders','economy_20mpg']].asfactor()

# Verify that the columns are now factors:
print(cars_df[['cylinders','economy_20mpg']].isfactor())
# [True, True]

If the column type is enum and you want to convert it to numeric, you should first convert it to character then convert it to numeric. Otherwise, the values may be converted to underlying factor values, not the expected mapped values.

# Using the data from the above example, convert the 'name' column  to numeric:
cars_df["name"] <- as.character(cars_df["name"])
cars_df["name"] <- as.numeric(cars_df["name"])

# Using the data from the above example, convert the 'name' column  to numeric:
cars_df['name'] = cars_df['name'].ascharacter().asnumeric()