feat: update readme (#9)

README.md

@@ -7,3 +7,57 @@ Rust setup for new project
 [![Docs](https://docs.rs/rs-stats/badge.svg)](https://docs.rs/rs-stats)
 [![Crates.io](https://img.shields.io/crates/v/rs-stats.svg)](https://crates.io/crates/rs-stats)
 [![crates.io](https://img.shields.io/crates/d/rs-stats)](https://crates.io/crates/rs-stats)
+
+
+rs-stats: A Rust Statistics Library
+
+This library provides a collection of statistical functions implemented in Rust. It aims to offer a simple and efficient way to perform common statistical calculations.
+
+Features:
+
+- Error Functions:
+    - erf(x: f64) -> f64: Calculates the error function of a given value.
+    - erfc(x: f64) -> f64: Calculates the complementary error function of a given value.
+
+- Normal Distribution:
+    - normal_cummulative_distrib(z: f64) -> f64: Calculates the cumulative distribution function (CDF) of the standard normal distribution.
+    - normal_probability_density(z: f64) -> f64: Calculates the probability density function (PDF) of the standard normal distribution.
+
+- Descriptive Statistics:
+    - average(data: &[f64]) -> f64: Calculates the average (mean) of a dataset.
+    - stddev(data: &[f64]) -> f64: Calculates the population standard deviation of a dataset.
+    - variance(data: &[f64]) -> f64: Calculates the population variance of a dataset.
+
+- Other:
+    - z_score(x: f64, avg: f64, stddev: f64) -> f64: Calculates the z-score of a value given the mean and standard deviation.
+    - cummulative_distrib(x: f64, avg: f64, stddev: f64) -> f64: Calculates the cumulative distribution function (CDF) of a normal distribution with a given mean and standard deviation.
+    - probability_density(x: f64, avg: f64, stddev: f64) -> f64: Calculates the probability density function (PDF) of a normal distribution with a given mean and standard deviation.
+    - std_err(data: &[f64]) -> f64: Calculates the standard error of the mean.
+
+Usage:
+
+Add this to your Cargo.toml:
+
+[dependencies]
+rs-stats = "0.3.0" # Replace with the actual version
+
+Then, in your Rust code:
+
+use rs_stats::average; // Import the function
+
+```
+fn main() {
+    let data = vec![1.0, 2.0, 3.0, 4.0, 5.0];
+    let avg = average(&data);
+    println!("Average: {}", avg);
+}
+```
+
+Contributing:
+
+Contributions are welcome! Feel free to open issues or submit pull requests.
+
+License:
+
+This project is licensed under the MIT License - see the LICENSE   
+ file for details.