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Why does the output have Nulls? (was: Help me, please!)

Posted 10 years ago

Can somebody explain to me that means this result, please? I want to solve a equation of grade six and the result is:

N1n/. {Null (n->-0.000668656)}
N2n/. {Null (n->0.000861383)}
N3n/. {{Null (n->-0.0122202)},{Null (n->0.000861383)}}[[3]]
N4n/. {{Null (n->-0.0122202)},{Null (n->0.000861383)}}[[4]]
N5n/. {{Null (n->-0.0122202)},{Null (n->0.000861383)}}[[5]]
N6n/. {{Null (n->-0.0122202)},{Null (n->0.000861383)}}[[6]]

I can't understand it!

Thanks very much.

POSTED BY: Maria Luisa
4 Replies

And a suggestion. Please change the title of your post. Post titles should have something that indicates what the question is not just a cry for help.

POSTED BY: David Reiss
Posted 10 years ago

Hello Maria, without the code that produced that output we can only guess. Maybe you forgot a semicolon somewhere?

POSTED BY: Gustavo Delfino
Posted 2 years ago

I have been running my code successfully, but now when I run it the code outputs Null and it is not supposed to because I did not change anything. I quit the local kernel, but is still outputs Null, somewhere it outputs Null^3. From this:

Out[38]: {t, x, u}
Out[39]: {{1/A^2, (d x)/A^2, (F u)/A^2}, {0, x, 0}, {2 t, 
  x (d t + Log[x]), (-(1/2) + 2 F t) u}, {0, A^2 t x, 
  u (-d t + Log[x])}, {A^2 t^2, A^2 t x Log[x], 
  1/2 u (-A^2 t + 2 A^2 F t^2 + (-d t + Log[x])^2)}, {0, 0, u}}
Out[40]: {A, d, F}
Out[48]: {{{0, 0, 2, 0, 0, 0}, {0, 0, 0, 0, 0, 0}, {-2, 0, 0, 0, 0, 0}, {0, 0, 
   0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}}, {{0, 0, 0, 1,
    0, 0}, {0, 0, 1, 0, 0, 0}, {0, -1, 0, 0, 0, 0}, {-1, 0, 0, 0, 0, 
   0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}}, {{0, 0, 0, 0, 1, 
   0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 
   0}, {-1, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}}, {{0, 0, 0, 0, 0, 
   0}, {0, 0, 0, 0, 1, 0}, {0, 0, 0, 1, 0, 0}, {0, 0, -1, 0, 0, 
   0}, {0, -1, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}}, {{0, 0, 0, 0, 0, 
   0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 2, 0}, {0, 0, 0, 0, 0, 0}, {0,
    0, -2, 0, 0, 0}, {0, 0, 0, 0, 0, 0}}, {{0, 0, 0, 0, 0, 0}, {0, 0, 
   0, 1, 0, 0}, {0, 0, 0, 0, 0, 0}, {0, -1, 0, 0, 0, 0}, {0, 0, 0, 0, 
   0, 0}, {0, 0, 0, 0, 0, 0}}}

To this: Out[38]: {Null t, Null x, Null u}
Out[39]: {{Null^2, Null, (F u)/A^2}, {0, x, 0}, {2 t, 
  x (d t + Log[x]), (-(1/2) + 2 F t) u}, {0, A^2 t x, 
  u (-d t + Log[x])}, {A^2 t^2, A^2 t x Log[x], 
  1/2 u (-A^2 t + 2 A^2 F t^2 + (-d t + Log[x])^2)}, {0, 0, u}}
Out[40]: {Null^3, Null, Null^3
Out[48]: {{{0, 0, 2, null, 0, 0}, {0, 0, null, 0, 0, 0}, {-2,null, 0, 0, 0, 0}, {0, 0, 
   0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}}, {{0, 0, 0, 1,
    0, 0}, {0, 0, 1, 0,null, 0}, {0, -1, 0, 0, 0, 0}, {-1, 0, 0, null, 0, 
   0}, {0, 0, 0, 0, null, 0}, {0, 0, 0, 0, 0, null}}, {{0, 0, 0, 0, 1, 
   0}, {0, 0, null, 0, 0, 0}, {0, 0, 0, 0,null, 0}, {0, 0, 0, 0, 0, 
   0}, {-1, 0, 0, 0, 0, 0}, {0, null, 0, 0, 0, 0}}, {{0, 0, 0, 0, 0, 
   0}, {0, 0, 0, 0, 1, null}, {0, 0, 0, 1, 0, 0}, {0, 0, -1, 0, 0, 
   0}, {0, -1, 0, 0, 0, 0}, {0, 0, 0, 0, null, 0}}, {{0, 0, 0, null, 0, 
   0}, {0, 0, 0, null, 0, 0}, {0, 0, 0, 0, 2, 0}, {0, 0, 0, 0, 0, 0}, {0,
    0, -2, 0, 0, 0}, {0, 0, 0, 0, 0, 0}}, {{0, 0, 0, 0, 0, 0}, {0, 0, 
   0, 1, 0, 0}, {0, 0, 0, 0, 0, 0}, {0, null, 0, 0, 0, 0}, {0, 0, 0, 0, 
   0, 0}, {0, 0, 0, null, 0, 0}}}

What could be the problem?

POSTED BY: Nomsa Ledwaba
Posted 2 years ago

Saying that a Null appeared where it didn't appear before just isn't enough information for us to help. We really need to see the code that causes this. The simplest code that reproduces the problem would be best, but anything at all would help us avoid shooting in the dark.

POSTED BY: Eric Rimbey
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