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# Arange

An Arange NumPy array is an array of equally spaced values determined by a step size between values.

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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.arange() to create an array of values starting from the start value and incrementally going up to end value by incrementing up by the step value. step is by default set to 1. It is very similar to np.linspace as both output arrays which start and stop at given values and with a certain number of values in the array, or rather, with a step size that gets us from the start to the end.

In [2]:
np.arange(0, 10)

Out[2]:
array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])

#### Making a Plot¶

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

x = np.arange(0, 100)
y = np.arange(0, 200, 2)

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

Out[3]:
In [4]:
help(np.arange)

Help on built-in function arange in module numpy.core.multiarray:

arange(...)
arange([start,] stop[, step,], dtype=None)

Return evenly spaced values within a given interval.

Values are generated within the half-open interval [start, stop)
(in other words, the interval including start but excluding stop).
For integer arguments the function is equivalent to the Python built-in
range <http://docs.python.org/lib/built-in-funcs.html>_ function,
but returns an ndarray rather than a list.

When using a non-integer step, such as 0.1, the results will often not
be consistent.  It is better to use linspace for these cases.

Parameters
----------
start : number, optional
Start of interval.  The interval includes this value.  The default
start value is 0.
stop : number
End of interval.  The interval does not include this value, except
in some cases where step is not an integer and floating point
round-off affects the length of out.
step : number, optional
Spacing between values.  For any output out, this is the distance
between two adjacent values, out[i+1] - out[i].  The default
step size is 1.  If step is specified, start must also be given.
dtype : dtype
The type of the output array.  If dtype is not given, infer the data
type from the other input arguments.

Returns
-------
arange : ndarray
Array of evenly spaced values.

For floating point arguments, the length of the result is
ceil((stop - start)/step).  Because of floating point overflow,
this rule may result in the last element of out being greater
than stop.

--------
linspace : Evenly spaced numbers with careful handling of endpoints.
ogrid: Arrays of evenly spaced numbers in N-dimensions.
mgrid: Grid-shaped arrays of evenly spaced numbers in N-dimensions.

Examples
--------
>>> np.arange(3)
array([0, 1, 2])
>>> np.arange(3.0)
array([ 0.,  1.,  2.])
>>> np.arange(3,7)
array([3, 4, 5, 6])
>>> np.arange(3,7,2)
array([3, 5])


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