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# Exponential Fit in Python

Create a exponential fit / regression in Python and add a line of best fit to your chart.

#### New to Plotly?¶

Plotly's Python library is free and open source! Get started by downloading the client and reading the primer.
You can set up Plotly to work in online or offline mode, or in jupyter notebooks.
We also have a quick-reference cheatsheet (new!) to help you get started!

#### Version Check¶

Note: exponential fits are available in version 1.9.2+
Run pip install plotly --upgrade to update your Plotly version

In [1]:
import plotly
plotly.__version__

Out[1]:
'1.12.12'

### Exponential Fit¶

In [2]:
# Learn about API authentication here: https://plot.ly/python/getting-started
# Find your api_key here: https://plot.ly/settings/api

import plotly.plotly as py
import plotly.graph_objs as go

# Scientific libraries
import numpy as np
from scipy.optimize import curve_fit

x = np.array([399.75, 989.25, 1578.75, 2168.25, 2757.75, 3347.25, 3936.75, 4526.25, 5115.75, 5705.25])
y = np.array([109,62,39,13,10,4,2,0,1,2])

def exponenial_func(x, a, b, c):
return a*np.exp(-b*x)+c

popt, pcov = curve_fit(exponenial_func, x, y, p0=(1, 1e-6, 1))

xx = np.linspace(300, 6000, 1000)
yy = exponenial_func(xx, *popt)

# Creating the dataset, and generating the plot
trace1 = go.Scatter(
x=x,
y=y,
mode='markers',
marker=go.Marker(color='rgb(255, 127, 14)'),
name='Data'
)

trace2 = go.Scatter(
x=xx,
y=yy,
mode='lines',
marker=go.Marker(color='rgb(31, 119, 180)'),
name='Fit'
)

annotation = go.Annotation(
x=2000,
y=100,
text='$\textbf{Fit}: 163.56e^{-0.00097x} - 1.16$',
showarrow=False
)
layout = go.Layout(
title='Exponential Fit in Python',
plot_bgcolor='rgb(229, 229, 229)',
xaxis=go.XAxis(zerolinecolor='rgb(255,255,255)', gridcolor='rgb(255,255,255)'),
yaxis=go.YAxis(zerolinecolor='rgb(255,255,255)', gridcolor='rgb(255,255,255)'),
annotations=[annotation]
)

data = [trace1, trace2]
fig = go.Figure(data=data, layout=layout)

py.plot(fig, filename='Exponential-Fit-in-python')

Out[2]:
u'https://plot.ly/~PythonPlotBot/164'
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