How to | Get Elements of Lists

Lists are very important structures in the Wolfram Language. Lists allow you to treat any kind of collection of objects as a single entity. Sometimes you need to pick out or extract individual elements or groups of elements from a list.

Set up a list of the first 10 squares (stored as ):

In[1]:=
Click for copyable input
Out[1]=

Use Part to pick the third element of the list:

In[2]:=
Click for copyable input
Out[2]=

Or use (the short form notation for Part):

In[3]:=
Click for copyable input
Out[3]=

Combine (the short form for Span) with Part to pick out the elements from 1 to 5:

In[4]:=
Click for copyable input
Out[4]=

Pick out elements 5 through 8 of the list:

In[5]:=
Click for copyable input
Out[5]=

Pick the last 7 elements (negative indices count from the end):

In[6]:=
Click for copyable input
Out[6]=
    

A matrix in the Wolfram Language is a list of lists of the same length. You can pick out elements from a matrix just like you would from a list.

Set up a 5×5 matrix of integers:

In[1]:=
Click for copyable input
Out[1]=

Use MatrixForm to see it laid out as a matrix:

In[2]:=
Click for copyable input
Out[2]//MatrixForm=

The first part of the matrix is the first row:

In[3]:=
Click for copyable input
Out[3]=