Skip to main content

Contextual Precision

The contextual precision metric measures your RAG pipeline's retriever by evaluating whether nodes in your retrieval_context that are relevant to the given input are ranked higher than irrelevant ones. deepeval's contextual precision metric is a self-explaining LLM-Eval, meaning it outputs a reason for its metric score.

Required Arguments​

To use the ContextualPrecisionMetric, you'll have to provide the following arguments when creating an LLMTestCase:

  • input
  • actual_output
  • expected_output
  • retrieval_context

Example​

from deepeval import evaluate
from deepeval.metrics import ContextualPrecisionMetric
from deepeval.test_case import LLMTestCase

# Replace this with the actual output from your LLM application
actual_output = "We offer a 30-day full refund at no extra cost."

# Replace this with the expected output from your RAG generator
expected_output = "You are eligible for a 30 day full refund at no extra cost."

# Replace this with the actual retrieved context from your RAG pipeline
retrieval_context = ["All customers are eligible for a 30 day full refund at no extra cost."]

metric = ContextualPrecisionMetric(
    threshold=0.7,
    model="gpt-4",
    include_reason=True
)
test_case = LLMTestCase(
    input="What if these shoes don't fit?",
    actual_output=actual_output,
    expected_output=expected_output,
    retrieval_context=retrieval_context
)

metric.measure(test_case)
print(metric.score)
print(metric.reason)

# or evaluate test cases in bulk
evaluate([test_case], [metric])

There are three optional parameters when creating a ContextualPrecisionMetric:

  • [Optional] threshold: a float representing the minimum passing threshold, defaulted to 0.5.
  • [Optional] model: a string specifying which of OpenAI's GPT models to use, OR any one of langchain's chat models of type BaseChatModel. Defaulted to 'gpt-4-1106-preview'.
  • [Optional] include_reason: a boolean which when set to True, will include a reason for its evaluation score. Defaulted to True.

You can also choose to fallback to Ragas' contextual precision metric (which has a similar implemention). This however is not capable of generating a reason.

from deepeval.metrics.ragas import RAGASContextualPrecisionMetric