@acer Thank you very much

Due to  your advise and code, now I can handle to my problems.

@acer Firts of all, I appreciate the fast reply,

I am so sorry my primitive question.

My problem is that ; I have a huge nested list about graph name and its  eigenvalues, I have to group the nested list via eigenvalues.

I know that ListTools and classify, group , categorize  commands but I still fixed my problems because of the eigenvalues are also list,

To Illustrate my purpose I can give a pseudo exam:

MyNestedList = [   [g1, [1,2,3]]     ,   [g2, [0,1,3]]   ,  [g3, [1,2,3]]  ,  [g4, [0,1,3]]  , ...    ]

GroupedList  = [   [ [1,2,3] , [ g1,g3]]    ,    [ [0,1,3] , [ g2,g4]]   ,. ...                              ]

@tomleslie thank you very much

@Markiyan Hirnyk I have studyed about mathametic modelling, i know that we can set edge weight by MakeWeighted(G) but i have to give a weight to vertex in Graph. i dont know how can i make this...

for example Set of Vertices={v1,v2,..Vn}  

weight of vertex1= arbitrary number

@tomleslie thanx

@tomleslie Thank you so much

i have lots of worksheets on maple 18 and i can not work on maple 2016 

standard worksheet interface not active...

i will send a screenphoto,

execute comment not work