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| 1 | +--- |
| 2 | +jupyter: |
| 3 | + jupytext: |
| 4 | + notebook_metadata_filter: all |
| 5 | + text_representation: |
| 6 | + extension: .md |
| 7 | + format_name: markdown |
| 8 | + format_version: '1.1' |
| 9 | + jupytext_version: 1.1.1 |
| 10 | + kernelspec: |
| 11 | + display_name: Python 3 |
| 12 | + language: python |
| 13 | + name: python3 |
| 14 | + language_info: |
| 15 | + codemirror_mode: |
| 16 | + name: ipython |
| 17 | + version: 3 |
| 18 | + file_extension: .py |
| 19 | + mimetype: text/x-python |
| 20 | + name: python |
| 21 | + nbconvert_exporter: python |
| 22 | + pygments_lexer: ipython3 |
| 23 | + version: 3.6.8 |
| 24 | + plotly: |
| 25 | + description: Add linear Ordinary Least Squares (OLS) regression trendlines or non-linear |
| 26 | + Locally Weighted Scatterplot Smoothing (LOEWSS) trendlines to scatterplots in Python. |
| 27 | + display_as: statistics |
| 28 | + language: python |
| 29 | + layout: base |
| 30 | + name: Linear and Non-Linear Trendlines |
| 31 | + order: 10 |
| 32 | + page_type: u-guide |
| 33 | + permalink: python/linear-fits/ |
| 34 | + thumbnail: thumbnail/linear_fit.jpg |
| 35 | +--- |
| 36 | + |
| 37 | +### Linear fit trendlines with Plotly Express |
| 38 | + |
| 39 | +[Plotly Express](/python/plotly-express/) is the easy-to-use, high-level interface to Plotly, which [operates on "tidy" data](/python/px-arguments/). |
| 40 | + |
| 41 | +Plotly Express allows you to add [Ordinary Least](https://en.wikipedia.org/wiki/Ordinary_least_squares) Squares regression trendline to scatterplots with the `trendline` argument. In order to do so, you will need to install `statsmodels` and its dependencies. Hovering over the trendline will show the equation of the line and its R-squared value. |
| 42 | + |
| 43 | + |
| 44 | +```python |
| 45 | +import plotly.express as px |
| 46 | + |
| 47 | +tips = px.data.tips() |
| 48 | +fig = px.scatter(tips, x="total_bill", y="tip", trendline="ols") |
| 49 | +fig.show() |
| 50 | +``` |
| 51 | + |
| 52 | +### Fitting multiple lines and retrieving the model parameters |
| 53 | + |
| 54 | +Plotly Express will fit a trendline per trace, and allows you to access the underlying model parameters for all the models. |
| 55 | + |
| 56 | +```python |
| 57 | +import plotly.express as px |
| 58 | + |
| 59 | +tips = px.data.tips() |
| 60 | +fig = px.scatter(tips, x="total_bill", y="tip", facet_col="smoker", color="sex", trendline="ols") |
| 61 | +fig.show() |
| 62 | + |
| 63 | +results = px.get_trendline_results(fig) |
| 64 | +print(results) |
| 65 | + |
| 66 | +results.query("sex == 'Male' and smoker == 'Yes'").px_fit_results.iloc[0].summary() |
| 67 | +``` |
| 68 | + |
| 69 | +### Non-Linear Trendlines |
| 70 | + |
| 71 | +Plotly Express also supports non-linear [LOWESS](https://en.wikipedia.org/wiki/Local_regression) trendlines. |
| 72 | + |
| 73 | +```python |
| 74 | +import plotly.express as px |
| 75 | + |
| 76 | +gapminder = px.data.gapminder().query("year == 2007") |
| 77 | +fig = px.scatter(gapminder, x="gdpPercap", y="lifeExp", color="continent", trendline="lowess") |
| 78 | +fig.show() |
| 79 | +``` |
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