Basic Examples (4) 

Select positions that have even elements:

In[1]:=

Out[1]=

Use a pure function to test each element:

In[2]:=

Out[2]=

Return only the first position selected:

In[3]:=

Out[3]=

Use the operator form of SelectPositions:

In[4]:=

Out[4]=

SelectPositions operates on values in an Association:

In[5]:=

Out[5]=

Scope (4) 

SelectPositions picks out positions for which applying the criterion explicitly yields True:

In[6]:=

Out[6]=

Applying the criterion to the symbolic object x does not explicitly yield True:

In[7]:=

Out[7]=

Find positions of pairs containing x:

In[8]:=

Out[8]=

Find up to two pairs containing x:

In[9]:=

Out[9]=

Fewer than the requested elements may be returned:

In[10]:=

Out[10]=

Use an operator form as selection criterion:

In[11]:=

Out[11]=

Use SelectPositions in operator form:

In[12]:=

Out[12]=

Generalizations and Extensions (2) 

SelectPositions works with any head, not just List:

In[13]:=

Out[13]=

SelectPositions works with SparseArray objects:

In[14]:=

Out[14]=

In[15]:=

Out[15]=

In[16]:=

Out[16]=

Applications (5) 

Get positions of elements that match a criterion for use in other functions:

In[17]:=

Out[17]=

In[18]:=

Out[18]=

Use with Extract:

In[19]:=

Out[19]=

Use with ReplacePart:

In[20]:=

Out[20]=

Use with MapAt:

In[21]:=

Out[21]=

Use with Insert:

In[22]:=

Out[22]=

Properties and Relations (3) 

SelectPositions is similar to Position except that it uses a function instead of a pattern:

In[23]:=

Out[23]=

Select the position of lists that have a sum of elements less than 10:

In[24]:=

Out[25]=

Use Position to get the same result:

In[26]:=

Out[26]=