Show Sidebar Hide Sidebar

# Append

How to add values to the end of a NumPy array.

#### New to Plotly?¶

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!

### Imports¶

This tutorial imports Plotly and Numpy.

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

import numpy as np


#### Append Data¶

Very similar in application to the core Python list method .append(), the np.append() function takes an array and some values in the form of an array and extends the length of the given array and adds the given item at the end.

In [2]:
import plotly.plotly as py
import plotly.graph_objs as go

array = np.array([1, 2, 3, 4, 5])
longer_array = np.append(array, [6, 7, 8])

trace1 = go.Scatter(
x=array,
y=[1 for i in array],
mode='markers',
marker=dict(
size=[5 + 3*j for j in array]
),
name='array'
)
trace2 = go.Scatter(
x=longer_array,
y=[2 for j in longer_array],
mode='markers',
marker=dict(
size=[5 + 3*j for j in longer_array]
),
name='longer_array'
)

py.iplot([trace1, trace2], filename='numpy-append')

Out[2]:
In [3]:
help(np.append)

Help on function append in module numpy.lib.function_base:

append(arr, values, axis=None)
Append values to the end of an array.

Parameters
----------
arr : array_like
Values are appended to a copy of this array.
values : array_like
These values are appended to a copy of arr.  It must be of the
correct shape (the same shape as arr, excluding axis).  If
axis is not specified, values can be any shape and will be
flattened before use.
axis : int, optional
The axis along which values are appended.  If axis is not
given, both arr and values are flattened before use.

Returns
-------
append : ndarray
A copy of arr with values appended to axis.  Note that
append does not occur in-place: a new array is allocated and
filled.  If axis is None, out is a flattened array.

--------
insert : Insert elements into an array.
delete : Delete elements from an array.

Examples
--------
>>> np.append([1, 2, 3], [[4, 5, 6], [7, 8, 9]])
array([1, 2, 3, 4, 5, 6, 7, 8, 9])

When axis is specified, values must have the correct shape.

>>> np.append([[1, 2, 3], [4, 5, 6]], [[7, 8, 9]], axis=0)
array([[1, 2, 3],
[4, 5, 6],
[7, 8, 9]])
>>> np.append([[1, 2, 3], [4, 5, 6]], [7, 8, 9], axis=0)
Traceback (most recent call last):
...
ValueError: arrays must have same number of dimensions


Still need help?