Basic Examples
Basic Examples
Create a list of the positive integers corresponding to letters “a” to “j”:
[CharacterRange["a","j"]]
In[]:=
{1,2,3,4,5,6,7,8,9,10}
Out[]=
Create a list of integers starting with 5 and incrementing by 2 each time that correspond to the letters "a" to "j":
[CharacterRange["a","j"],5,2]
In[]:=
{5,7,9,11,13,15,17,19,21,23}
Out[]=
Create an operator which, when it an expression, creates a list with the same number of parts as that expression, in which the first element is 1, and in which each successive value is 1 higher:
[1,1][CharacterRange["a","j"]]
In[]:=
{1,2,3,4,5,6,7,8,9,10}
Out[]=
Scope
Scope
The function works on expressions that are not lists :
[a[b,c,d]]
In[]:=
{1,2,3}
Out[]=
Because the length of an is equal to its number of key value pairs, the function can be sensibly applied to associations:
[Association["a"6,"b"9]]
In[]:=
{1,2}
Out[]=
The function looks only at the first level of an expression to determine the correspondence :
[IdentityMatrix[7]]
In[]:=
{1,2,3,4,5,6,7}
Out[]=
Using non - integer values for the starting value and/or the jump will give a warning, as this is not the purpose for which the function is intended:
[CharacterRange["a","z"],4.5,2]
IntegerCorrespondence
{4.5,6.5,8.5,10.5,12.5,14.5,16.5,18.5,20.5,22.5,24.5,26.5,28.5,30.5,32.5,34.5,36.5,38.5,40.5,42.5,44.5,46.5,48.5,50.5,52.5,54.5}
Out[]=
Applications
Applications
Use CorrespondingIntegers to develop indices into a training and test set used for machine learning:
SeedRandom[1];ModuleallIndices=
[{\[LeftAssociation]"sex""female","survived"True\[RightAssociation],\[LeftAssociation]"sex""male","survived"True\[RightAssociation],\[LeftAssociation]"sex""female","survived"False\[RightAssociation],\[LeftAssociation]"sex""male","survived"False\[RightAssociation],\[LeftAssociation]"sex""female","survived"False\[RightAssociation],\[LeftAssociation]"sex""male","survived"True\[RightAssociation],\[LeftAssociation]"sex""female","survived"True\[RightAssociation],\[LeftAssociation]"sex""male","survived"False\[RightAssociation],\[LeftAssociation]"sex""female","survived"True\[RightAssociation],\[LeftAssociation]"sex""male","survived"False\[RightAssociation]}],trainingIndices,testIndices,trainingIndices=RandomSample[allIndices,7];testIndices=Complement[allIndices,trainingIndices];{trainingIndices,testIndices}
In[]:=
{{2,5,1,10,8,6,7},{3,4,9}}
Out[]=
Index the terms in some document both backwards and forwards:
Module{vocabulary=DeleteDuplicates[TextWords[ExampleData[{"Text","USConstitution"}]]],correspondence,threaded},correspondence=
[vocabulary];threaded=Thread[vocabularycorrespondence];{Dispatch[threaded],Dispatch[Reverse/@threaded]}
In[]:=
Dispatch,Dispatch
Out[]=
Properties and Relations
Properties and Relations
This function can be combined with to emulate the action of at level 1 where one takes the first part of the index:
MapIndexed[f[#1,#2[[1]]]&,{a,b,c},1]===With{expr={a,b,c}},Threadfexpr,
[expr]
In[]:=
True
Out[]=