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1.8.6 Adding, Removing and Modifying List Elements

Functions for adding and deleting elements in lists.

  • This gives a list with x prepended.
  • In[1]:= Prepend[{a, b, c}, x]


  • This adds x at the end.
  • In[2]:= Append[{a, b, c}, x]


  • This inserts x so that it becomes element number 2.
  • In[3]:= Insert[{a, b, c}, x, 2]


  • Negative numbers count from the end of the list.
  • In[4]:= Insert[{a, b, c}, x, -2]


  • Delete removes an element from the list.
  • In[5]:= Delete[{a, b, c, d}, 3]


    Modifying parts of lists.

  • This replaces the third element in the list with x.
  • In[6]:= ReplacePart[{a, b, c, d}, x, 3]


  • This replaces the first and fourth parts of the list. Notice the need for double lists in specifying multiple parts to replace.
  • In[7]:= ReplacePart[{a, b, c, d}, x, {{1}, {4}}]


  • Here is a

    identity matrix.
  • In[8]:= IdentityMatrix[3]


  • This replaces the component of the matrix by x

  • In[9]:= ReplacePart[%, x, {2, 2}]