# Description of the Tool

Create a command line tool in Python that reads a single CSV data file from a data directory provided as an argument and produces PNG plots that visualise the mean, minimum, maximum, and standard deviation for each column in the dataset.

# Assumptions

- The tool is invoked from the command line with a path to a data directory.
- The data directory contains a number of CSV files to process.
- The CSV file is tabular data with columns that can be analysed numerically.
- NumPy is available for statistical calculations.
- Matplotlib is available for generating plots.
- PNG is the required output image format.

# User Stories

- As a user, I want to provide a data directory as input so that the tool can locate the CSV files to process.
  - Acceptance criteria:
    - The tool accepts a directory path argument.
    - The tool identifies the CSV files within that directory.

- As a user, for each CSV file, I want the tool to calculate mean, minimum, maximum, and standard deviation values for each column so that I can understand the distribution of the data.
  - Acceptance criteria:
    - The tool produces values for mean, minimum, maximum, and standard deviation for each column.
    - The calculations are based on NumPy.

- As a user, I want the tool to create PNG plots for each CSV file so that I can visually inspect the calculated statistics.
  - Acceptance criteria:
    - The tool generates plot images in PNG format.
    - The plots represent mean, minimum, maximum, and standard deviation across columns.

- As a user, I want the plots saved to disk so that I can review them after the tool finishes.
  - Acceptance criteria:
    - The tool writes its plot outputs as files rather than only displaying them interactively.

# Success Metrics

- A user can run the tool with a data directory argument and obtain PNG plot files.
- The generated plots reflect the mean, minimum, maximum, and standard deviation for each column in a CSV file.
- The tool uses NumPy for statistical analysis and Matplotlib for plotting.
- The tool works without requiring manual post-processing of the output files.

# Out of Scope

- Supporting non-CSV input formats.
- Building a graphical user interface.
- Defining a specific plot style, layout, or naming convention beyond PNG output.
- Adding data cleaning, transformation, or advanced analytics beyond the requested summary statistics.