# Regression

**Note: all keys return the same input data for this challenge.**

Estimating a quantity from others is an important skill. In petrophysics, we often have missing logs, or missing samples. **Regression** is a way to predict those missing values, allowing us to make some other analysis or visualization with more data.

To get the data for this challenge, you need to provide a key, but it can be empty (or anything at all) because the input is always the same:

```
params = {'key': ''}
```

The data we have is a CSV and the first few rows (samples or records) looks like this:

```
Vp [m/s],Vs [m/s]
3269.40,1966.80
3794.00,2074.00
2238.85,817.91
3377.00,1490.00
3734.34,2404.42
5216.54,3123.36
5216.54,2795.28
```

The first column (the independent variable, or predictor) represents P-wave sonic velocity mesurements from core plugs, and the second column (the dependent variable, or response) represents S-wave velocities from the same samples; both measurements are in units of m/s. We would like to predict the S-wave velocities from the P-wave. In the language of machine learning, the first column will be `x` and the second will be `y`.

Some of the rows only have the predictor variable: the response is missing. These are the samples you must make predictions for.

For this challenge, you will be sending a 1D NumPy array or list of floats to the server as `answer`. You do not need to provide a question number (it will be ignored if you do):

```
params = {
    'answer': y_pred
}
```


## A quick reminder how this works

This document is formatted in [Markdown](https://daringfireball.net/projects/markdown/).

You can retrieve your data, which is always a string, by choosing a **`<KEY>`** (also a string). This ensures that you have different data from other people, so be creative. 

```
url = 'https://kata.scienxlab.org/challenge/regression'
params = {
    'key': <KEY>  # Replace <KEY> with your own string.
}
r = requests.get(url, params)
r.text
```

To answer question 1, change the `params`:

```
params = {
    'key': <KEY>,   # Use the same key you used to get your input.
    'question': 1,
    'answer': 1234  # Your answer; can be a float, int, list or array;
                    # the challenge description will tell you which.
}
```

To get a hint for a question, provide the question number but no answer:

```
params = {
    'question': 1,
}
```

[Complete instructions at kata.scienxlab.org](https://kata.scienxlab.org/challenge)

[An example notebook to get you started](https://gist.github.com/kwinkunks/50f11dac6ab7ff8c3e6c7b34536501a2)

----

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