Student Support Forum: 'Null in variable output' topicStudent Support Forum > General > Archives > "Null in variable output"

 Next Comment > Help | Reply To Topic
 Author Comment/Response Otto Murphy 03/30/09 7:29pm Hi, I have the following code which will be used with TreePlot to create a diagram like this: http://en.wikipedia.org/wiki/File:Poset6.jpg poset[n_] := Module[{a, i, z, subsets, b, subsub, w}, a = List @@ Table[FromCharacterCode[96 + i], {i, n}]; b = {}; For[i = n, i > 0, i--, subsets = Subsets[a, {i}]; For[z = 1, z <= Binomial[n, i], z++, Print[ b = Join[ b, (subsets[[z]] -> #) & /@ Subsets[subsets[[z]], {i - 1}]] ]; ]] b ] poset[2] The output looks like this: During evaluation of In[91]:= {{a,b}->{a},{a,b}->{b}} During evaluation of In[91]:= {{a,b}->{a},{a,b}->{b},{a}->{}} During evaluation of In[91]:= {{a,b}->{a},{a,b}->{b},{a}->{},{b}->{}} Out[92]= {Null ({"a", "b"} -> {"a"}), Null ({"a", "b"} -> {"b"}), Null ({"a"} -> {}), Null ({"b"} -> {})} My question is: what is that Null doing there? Why is it there? URL: ,

 Subject (listing for 'Null in variable output') Author Date Posted Null in variable output Otto Murphy 03/30/09 7:29pm Re: Null in variable output yehuda ben-s... 04/01/09 06:54am Re: Re: Null in variable output Otto Murphy 04/02/09 05:51am
 Next Comment > Help | Reply To Topic