# Use an an anonymous function with NestGraph?

Posted 5 months ago
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 Hey,I am currently in chapter 27 of the Wolfram Language Book and can't seem to grasp the list creation and handling in the NestGraph function. NestGraph[{2 #, 2 # + 1} &, 0, 4, VertexLabels -> All] To understand what the above does step by step I "extracted" a part: In[1]:= {2 #, 2 # + 1} &@{2, 3} Out[1]= {{4, 6}, {5, 7}} My questions: Shouldn't the output be {{4, 5}, {6, 7}}? Why is it the way it is? How does NestGraph handle the above output internally to construct the correct graph? Thank you very much!!!Tim
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Posted 5 months ago
 The argument to the pure function is {2, 3}, which is assigned to # 2 {2, 3} (* {4, 6} *) 2 {2, 3} + 1 (* {5, 7} *) Compare the output of the following for different values of n NestList[{2 #, 2 # + 1} &, 0, n] NestGraph[{2 #, 2 # + 1} &, 0, n, VertexLabels -> All] and you should be able to see how the graph "grows".
 Hey! Sorry to bother you again, but I'm still having problems understanding how NestGraph[] builds the tree.I understand the function and how it generates the lists, I just don't get how NestGraph[] traverses the lists?! Please find attached a note I created to understand the flow.My questions (please see attached image): How does NetGraph[] figure out to go from {1,3} to {2,6}? Are the list entries I tagged with a question mark not evaluated at all? I think I'm having problems seeing something obvious and in the end it's probably easy, but I really like to understand.Thank you very much!