Prompting Strategies

If you want to annotate textual data, you can use various prompting strategies. For an overview of common approaches, you can read a paper by Weber and Reichardt (2023). These strategies primarily differ in whether or how many examples are given (Zero-shot, One-shot, or Few-shot) and whether reasoning is involved (Chain-of-Thought).

When writing a prompt we can give the model content for the system part, user part and assistant part. The system message typically includes instructions or context that guides the interaction, setting the stage for how the user and the assistant should interact. For an annotation task we could write: “You assign texts into categories. Answer with just the correct category.” The table below summarizes different prompting strategies for annotating textual data. Each strategy varies in the number of examples given and the incorporation of reasoning.

Prompting Strategy	Example Structure
Zero-shot	`{"role": "system", "content": "Text of System Prompt"},` `{"role": "user", "content": "(Text to classify) + classification question"}`
One-shot	`{"role": "system", "content": "Text of System Prompt"},` `{"role": "user", "content": "(Example text) + classification question"},` `{"role": "assistant", "content": "Example classification"},` `{"role": "user", "content": "(Text to classify) + classification question"}`
Few-shot	`{"role": "system", "content": "Text of System Prompt"},` `{"role": "user", "content": "(Example text) + classification question"},` `{"role": "assistant", "content": "Example classification"},` `{"role": "user", "content": "(Example text) + classification question"},` `{"role": "assistant", "content": "Example classification"},` `. . . more examples` `{"role": "user", "content": "(Text to classify) + classification question"}`
Chain-of-Thought	`{"role": "system", "content": "Text of System Prompt"},` `{"role": "user", "content": "(Text to classify) + reasoning question"},` `{"role": "assistant", "content": "Reasoning"},` `{"role": "user", "content": "Classification question"}`

Zero-shot

In this approach, no prior examples are given. The structure includes a system prompt providing instructions and a user prompt with the text to classify and the classification question (in this example we only provide the categories).

library(tibble)
library(purrr)
q <- tribble(
  ~role,    ~content,
  "system", "You assign texts into categories. Answer with just the correct category.",
  "user",   "text: the pizza tastes terrible\ncategories: positive, neutral, negative"
)
query(q)
#> 
#> ── Answer from llama3.2:3b-instruct-q8_0 ─────────────────────────────
#> negative

One-shot

This involves giving a single example before the actual task. The structure includes a system prompt, followed by a user prompt with an example text and classification question, the assistant’s example classification, and then another user prompt with the new text to classify.

q <- tribble(
  ~role,    ~content,
  "system", "You assign texts into categories. Answer with just the correct category.",
  "user", "text: the pizza tastes terrible\ncategories: positive, neutral, negative",
  "assistant", "Category: Negative",
  "user", "text: the service is great\ncategories: positive, neutral, negative"
)
query(q)
#> 
#> ── Answer from llama3.2:3b-instruct-q8_0 ─────────────────────────────
#> Category: Positive

A nice side effect of the one-shot strategy (and all n>0-strategies) is that you can tune the format the model uses in its replies. For example, if you want to have an output that easy to parse, you could change the assistant message to "{'Category':'Negative'}"

q <- tribble(
  ~role,    ~content,
  "system", "You assign texts into categories. Answer with just the correct category.",
  "user", "text: the pizza tastes terrible\ncategories: positive, neutral, negative",
  "assistant", "{'Category':'Negative'}",
  "user", "text: the service is great\ncategories: positive, neutral, negative"
)
answer <- query(q)
#> 
#> ── Answer from llama3.2:3b-instruct-q8_0 ─────────────────────────────
#> {'Category':'Positive'}

This is a valid JSON return and can be parsed into a list with, e.g., jsonlite::fromJSON(). Using this logic, we could request a more informative output:

q <- tribble(
  ~role,    ~content,
  "system", "You assign texts into categories. Provide the following information: category, confidence, and the word that is most important for your coding decision.",
  "user", "text: the pizza tastes terrible\ncategories: positive, neutral, negative",
  "assistant", "{'Category':'Negative','Confidence':'100%','Important':'terrible'}",
  "user", "text: the service is great\ncategories: positive, neutral, negative"
)
answer <- query(q)
#> 
#> ── Answer from llama3.2:3b-instruct-q8_0 ─────────────────────────────
#> {'Category':'Positive','Confidence':'100%','Important':'great'}

By using pluck(answer, "message", "content"), you can directly extract the result and don’t need to copy it from screen.

Few-shot

This strategy includes multiple examples (more than one). The structure is similar to one-shot but with several iterations of user and assistant messages providing examples before the final text to classify.

q <- tribble(
  ~role,    ~content,
  "system", "You assign texts into categories. Answer with just the correct category.",
  "user", "text: the pizza tastes terrible\ncategories: positive, neutral, negative",
  "assistant", "Category: Negative",
  "user", "text: the service is great\ncategories: positive, neutral, negative",
  "assistant", "Category: Positive",
  "user", "text: I once came here with my wife\ncategories: positive, neutral, negative",
  "assistant", "Category: Neutral",
  "user", "text: I once ate pizza\ncategories: positive, neutral, negative"
)
query(q)
#> 
#> ── Answer from llama3.2:3b-instruct-q8_0 ─────────────────────────────
#> Category: Neutral

Chain-of-Thought

This approach involves at least one reasoning step. The structure here starts with the system prompt, then a user prompt with a text to classify and a reasoning question.

q_thought <- tribble(
  ~role,    ~content,
  "system", "You assign texts into categories. ",
  "user",   "text: the pizza tastes terrible\nWhat sentiment (positive, neutral, or negative) would you assign? Provide some thoughts."
)
output_thought <- query(q_thought, output = "text")
#> 
#> ── Answer from llama3.2:3b-instruct-q8_0 ─────────────────────────────
#> I would assign a negative sentiment to this text.
#> 
#> Here's why:
#> 
#> * The word "terrible" is a strong adjective that conveys a strong
#> negative opinion.
#> * The tone of the sentence is also quite critical and dismissive.
#> * There are no positive or neutral phrases in the text, which
#> suggests that the author has a clear dislike for the pizza.
#> 
#> Overall, the language and tone used in this text indicate a strong
#> negative sentiment towards the pizza.

In the next step we can use the assistant’s reasoning and a user prompt with the classification question.

q <- tribble(
  ~role,    ~content,
  "system", "You assign texts into categories. ",
  "user",   "text: the pizza tastes terrible\nWhat sentiment (positive, neutral, or negative) would you assign? Provide some thoughts.",
  "assistant", output_thought,
  "user",   "Now answer with just the correct category (positive, neutral, or negative)"
)
resps <- query(q)
#> 
#> ── Answer from llama3.2:3b-instruct-q8_0 ─────────────────────────────
#> Negative

The `make_query` helper function

The make_query function is designed to facilitate the creation of a structured query for text classification, so that you do not need to build the tibble yourself and remember the specific structure.

Components:

text to Classify: The new text(s) to be annotated.
prompt: Classification question with the categories to be annotated.
template: Defines the structure for user messages. Defines the structure for user messages. The template can include placeholders like {text}, {prefix}, and {suffix} to dynamically format input.
system: System Prompt: Provides context or instructions for the classification task (optional).
prefix: A string to prepend to user queries (optional).
suffix: A string to append to user queries (optional).
examples: Prior examples consisting of user messages and assistant responses (for one-shot and few-shot learning)(optional).

Example usage

Zero-shot example

In this example, the function is used without any examples.

# Call the make_query function
q_zs <- make_query(
  template = "{text}\n{prompt}",
  text = "the pizza tastes terrible",
  prompt = "Categories: positive, neutral, negative",
  system = "You assign texts into categories. Answer with just the correct category.",
)

# Print the query
print(q_zs)
#> [[1]]
#> # A tibble: 2 × 2
#>   role   content                                                      
#>   <chr>  <glue>                                                       
#> 1 system You assign texts into categories. Answer with just the corre…
#> 2 user   the pizza tastes terrible
#> Categories: positive, neutral, nega…
# Run the query
query(q_zs)
#> 
#> ── Answer from llama3.2:3b-instruct-q8_0 ─────────────────────────────
#> negative

One-shot example

Here, one prior example is provided to aid the classification:

examples_os <- tibble::tribble(
  ~text, ~answer,
  "the pizza tastes terrible", "negative"
)

q_os <- make_query(
  text = "the service is great",
  template = "{text}\n{prompt}",
  prompt = "Categories: positive, neutral, negative",
  system = "You assign texts into categories. Answer with just the correct category.",
  example = examples_os,
)
print(q_os)
#> [[1]]
#> # A tibble: 4 × 2
#>   role      content                                                   
#>   <chr>     <glue>                                                    
#> 1 system    You assign texts into categories. Answer with just the co…
#> 2 user      the pizza tastes terrible
#> Categories: positive, neutral, n…
#> 3 assistant negative                                                  
#> 4 user      the service is great
#> Categories: positive, neutral, negati…

query(q_os)
#> 
#> ── Answer from llama3.2:3b-instruct-q8_0 ─────────────────────────────
#> positive

Few-shot example with multiple examples

This scenario uses multiple examples to enrich the context for the new classification:

examples_fs <- tibble::tribble(
  ~text, ~answer,
  "the pizza tastes terrible", "negative",
  "the service is great", "positive",
  "I once came here with my wife", "neutral"
)

q_fs <- make_query(
  text = "I once ate pizza",
  prompt = "Categories: positive, neutral, negative",
  template = "{text}\n{prompt}",
  system = "You assign texts into categories. Answer with just the correct category.",
  examples = examples_fs
)

query(q_fs)
#> 
#> ── Answer from llama3.2:3b-instruct-q8_0 ─────────────────────────────
#> neutral

Example using a dataframe

This example demonstrates how to perform sentiment analysis on a set of movie reviews. The process involves creating a dataframe of reviews, processing each review to classify its sentiment, and appending the results as a new column in the dataframe.

We create a dataframe named movie_reviews with two columns:

# Create an example dataframe with 5 movie reviews
movie_reviews <- tibble::tibble(
  review_id = 1:5,
  review = c("A stunning visual spectacle with a gripping storyline.",
             "The plot was predictable, but the acting was superb.",
             "An overrated film with underwhelming performances.",
             "A beautiful tale of love and adventure, beautifully shot.",
             "The movie lacked depth, but the special effects were incredible.")
)
# Print the initial dataframe
movie_reviews
#> # A tibble: 5 × 2
#>   review_id review                                                    
#>       <int> <chr>                                                     
#> 1         1 A stunning visual spectacle with a gripping storyline.    
#> 2         2 The plot was predictable, but the acting was superb.      
#> 3         3 An overrated film with underwhelming performances.        
#> 4         4 A beautiful tale of love and adventure, beautifully shot. 
#> 5         5 The movie lacked depth, but the special effects were incr…

We can use make_query again to define a query for each of these reviews. What we want to do is to perform a sentiment analysis, guided by a system message and a classification question.

# Process each review using make_query
queries <- make_query(
  text = movie_reviews$review,
  prompt = "Categories: positive, neutral, negative",
  template = "{prefix}{text}\n{prompt}",
  system = "Classify the sentiment of the movie review. Answer with just the correct category.",
  prefix = "Text to classify: "
)

This produces a list of data.frames that have the same query format we are now familiar with. All of them have the same prompt, system message and prefix, but each has a different text that came from the movie reviews data.frame we created above. The query function accepts lists of queries, so we can get the annotations simply using:

# Process and annotate the movie reviews
movie_reviews$annotation <- query(queries, screen = FALSE, output = "text")

# Print the annotated dataframe
movie_reviews
#> # A tibble: 5 × 3
#>   review_id review                                          annotation
#>       <int> <chr>                                           <chr>     
#> 1         1 A stunning visual spectacle with a gripping st… Positive  
#> 2         2 The plot was predictable, but the acting was s… positive  
#> 3         3 An overrated film with underwhelming performan… Negative  
#> 4         4 A beautiful tale of love and adventure, beauti… Positive  
#> 5         5 The movie lacked depth, but the special effect… Neutral

We can also use this approach in a ‘tidy’ coding style:

library(dplyr, warn.conflicts = FALSE)
movie_reviews_annotated <- movie_reviews |>
  mutate(
    sentiment = make_query(
      text = review,
      prompt = "Categories: positive, neutral, negative",
      template = "{prefix}{text}\n{prompt}",
      system = "Classify the sentiment of the movie review. Answer with just the correct category.",
      prefix = "Text to classify: "
    ) |>
      query(screen = FALSE, output = "text")
  )
movie_reviews_annotated
#> # A tibble: 5 × 4
#>   review_id review                                annotation sentiment
#>       <int> <chr>                                 <chr>      <chr>    
#> 1         1 A stunning visual spectacle with a g… Positive   Positive 
#> 2         2 The plot was predictable, but the ac… positive   positive 
#> 3         3 An overrated film with underwhelming… Negative   Negative 
#> 4         4 A beautiful tale of love and adventu… Positive   Positive 
#> 5         5 The movie lacked depth, but the spec… Neutral    Neutral

This takes a little longer than classic supervised machine learning or even classification with transformer models. However, the advantage is that instructions can be provided using plain English, the models need very few examples to perform surprisingly well, and the best models, like llama3.2, can often deal with more complex categories than other approaches.

annotation

Maximilian Weber and Johannes B. Gruber

Introduction

Prompting Strategies

Zero-shot

One-shot

Few-shot

Chain-of-Thought

The `make_query` helper function

Example usage

Zero-shot example

One-shot example

Few-shot example with multiple examples

Batch annotation

Example using a dataframe

annotation

Maximilian Weber and Johannes B. Gruber

Introduction

Prompting Strategies

Zero-shot

One-shot

Few-shot

Chain-of-Thought

The make_query helper function

Example usage

Zero-shot example

One-shot example

Few-shot example with multiple examples

Batch annotation

Example using a dataframe

The `make_query` helper function