Command Line Basics¶

This tutorial introduces Vowpal Wabbit command line basics with a quick introduction to training and testing your model with Vowpal Wabbit. We explore passing some data to Vowpal Wabbit to learn a model and get a prediction.

For more advanced Vowpal Wabbit tutorials, including how to format data and understand results, see Tutorials.

Prerequisites

To install Vowpal Wabbit see Get Started.

Training scenario and dataset¶

For this tutorial scenario, we want to use Vowpal Wabbit to help us predict whether or not a house will require a new roof in the next 10 years.

First, create a file train.txt and copy the following dataset:

| price:.23 sqft:.25 age:.05 2006
| price:.18 sqft:.15 age:.35 1976
| price:.53 sqft:.32 age:.87 1924

Note: If the format of this sample dataset looks unfamiliar and you want more details see the Vowpal Wabbit Linear Regression Tutorial for information on input format and feature hashing techniques.

Train a model¶

Next, we train a model, and save it to a file:

vw -d train.txt -f model.vw

This tells Vowpal Wabbit to:

Use the -d data file train.txt.
Write the -f final model to model.vw.

With Vowpal Wabbit, the output includes more than a few statistics and statuses. The Linear Regression Tutorial and Contextual Bandit Reinforcement Learning Tutorial covers this format in more detail:

Output:

final_regressor = model.vw
Num weight bits = 18
learning rate = 0.5
initial_t = 0
power_t = 0.5
using no cache
Reading datafile = train.txt
num sources = 1
average  since         example        example  current  current  current
loss     last          counter         weight    label  predict features
0.000000 0.000000            1            1.0   0.0000   0.0000        5
0.500000 1.000000            2            2.0   1.0000   0.0000        5

finished run
number of examples = 3
weighted example sum = 3.000000s
weighted label sum = 1.000000
average loss = 0.666667
best constant = 0.333333
best constant's loss = 0.222222
total feature number = 15

Test a model¶

Now, create a file called test.txt and copy this data:

| price:.46 sqft:.4 age:.10 1924

We get a prediction by loading the model and supplying our test data:

vw -d test.txt -i model.vw -p predictions.txt

This tells Vowpal Wabbit to:

Use the -d data file test.txt.
Use the -i input model model.vw.
Write -p predictions to predictions.txt.

Output:

predictions = predictions.txt
Num weight bits = 18
learning rate = 0.5
initial_t = 0
power_t = 0.5
using no cache
Reading datafile = test.txt
num sources = 1
average  since         example        example  current  current  current
loss     last          counter         weight    label  predict features
    n.a.     n.a.            1            1.0  unknown   0.0000        5

finished run
number of examples = 1
weighted example sum = 1.000000
weighted label sum = 0.000000
average loss = n.a.

cat predictions.txt shows:

Vowpal Wabbit results¶

The model predicted a value of 0. This result means our house will not need a new roof in the next 10 years (based on just three examples we used in our training dataset).

More to explore¶

See Python tutorial for a quick introduction to the basics of training and testing your model.
To learn more about how to approach a contextual bandits problem using Vowpal Wabbit — including how to work with different contextual bandits approaches, how to format data, and understand the results — see the Contextual Bandit Reinforcement Learning Tutorial.
For more on the contextual bandits approach to reinforcement learning, including a content personalization scenario, see the Contextual Bandit Simulation Tutorial.
See the Linear Regression Tutorial for a different look at the roof replacement problem and learn more about Vowpal Wabbit’s format and understanding the results.