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# Linspace

A Linspace Array is an array of equally spaced values going from a start to an end value.

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### Imports¶

This tutorial imports Plotly and Numpy.

In [1]:
import plotly.plotly as py
import plotly.graph_objs as go

import numpy as np


#### Simple Example¶

We can use np.linspace() to create an array of equally spaced values. By declaring a start value, stop value, and the num of points in between those points an array will be generated. For example, np.linspace(0, 1, 5) results in the following array:

In [2]:
np.linspace(0, 1, 5)

Out[2]:
array([ 0.  ,  0.25,  0.5 ,  0.75,  1.  ])

#### Making a Plot¶

In [3]:
import plotly.plotly as py
import plotly.graph_objs as go

x = np.linspace(0, 10, 250)
y = np.sin(x)

trace = go.Scatter(x=x, y=y, mode='markers')
py.iplot([trace], filename='numpy-linspace')

Out[3]:
In [4]:
help(np.linspace)

Help on function linspace in module numpy.core.function_base:

linspace(start, stop, num=50, endpoint=True, retstep=False, dtype=None)
Return evenly spaced numbers over a specified interval.

Returns num evenly spaced samples, calculated over the
interval [start, stop].

The endpoint of the interval can optionally be excluded.

Parameters
----------
start : scalar
The starting value of the sequence.
stop : scalar
The end value of the sequence, unless endpoint is set to False.
In that case, the sequence consists of all but the last of num + 1
evenly spaced samples, so that stop is excluded.  Note that the step
size changes when endpoint is False.
num : int, optional
Number of samples to generate. Default is 50. Must be non-negative.
endpoint : bool, optional
If True, stop is the last sample. Otherwise, it is not included.
Default is True.
retstep : bool, optional
If True, return (samples, step), where step is the spacing
between samples.
dtype : dtype, optional
The type of the output array.  If dtype is not given, infer the data
type from the other input arguments.

Returns
-------
samples : ndarray
There are num equally spaced samples in the closed interval
[start, stop] or the half-open interval [start, stop)
(depending on whether endpoint is True or False).
step : float
Only returned if retstep is True

Size of spacing between samples.

--------
arange : Similar to linspace, but uses a step size (instead of the
number of samples).
logspace : Samples uniformly distributed in log space.

Examples
--------
>>> np.linspace(2.0, 3.0, num=5)
array([ 2.  ,  2.25,  2.5 ,  2.75,  3.  ])
>>> np.linspace(2.0, 3.0, num=5, endpoint=False)
array([ 2. ,  2.2,  2.4,  2.6,  2.8])
>>> np.linspace(2.0, 3.0, num=5, retstep=True)
(array([ 2.  ,  2.25,  2.5 ,  2.75,  3.  ]), 0.25)

Graphical illustration:

>>> import matplotlib.pyplot as plt
>>> N = 8
>>> y = np.zeros(N)
>>> x1 = np.linspace(0, 10, N, endpoint=True)
>>> x2 = np.linspace(0, 10, N, endpoint=False)
>>> plt.plot(x1, y, 'o')
[<matplotlib.lines.Line2D object at 0x...>]
>>> plt.plot(x2, y + 0.5, 'o')
[<matplotlib.lines.Line2D object at 0x...>]
>>> plt.ylim([-0.5, 1])
(-0.5, 1)
>>> plt.show()


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