Updating a Vector in a For Loop: Troubleshooting Tips

[member 428835]

I am trying to update a vector. I have tried this but it's not working. Any ideas?

\[Lambda] = {1, 2}
For[\[CapitalLambda] = 0.1, \[CapitalLambda] <=
0.2, \[CapitalLambda] += 0.1, \[Lambda] =
Catenate[{\[Lambda], {\[CapitalLambda]}}] // Print]

 

[RPinPA]

Dumb question, but what language is this? I don't recognize the syntax.

Edit: Ah, just noticed the Mathematica tag. Sorry. Maybe someone more knowledgeable with Mathematica can figure it out.

What are you expecting to be the output? It looks like you intended Lambda to be concatenated with the values taken by CapitalLambda, so at the end it should look like {1, 2, 0.1, 0.2}?

 

[Dale]

I have tried this but it's not working.

What do you mean by “it’s not working”? What happens?

 

[jedishrfu]

Have you tried to simplify it to verify the loop itself works?

Is there a stepping debugger in mathematica that you can use to diagnose the issue?

 

[DrClaude]

\[Lambda] = {1, 2}
For[\[CapitalLambda] = 0.1, \[CapitalLambda] <=
0.2, \[CapitalLambda] += 0.1, \[Lambda] =
Catenate[{\[Lambda], {\[CapitalLambda]}}] // Print]

The // modifies what it operates on. What you get back from

\[Lambda] = Catenate[{\[Lambda], {\[CapitalLambda]}}] // Print

is not λ but a Null,

Edit: the above is not well formulated. What I mean is that what is on the right-hand-side returns Null, so it is equivalent to λ = NullIn[16]:= FullForm[Sqrt[2]]
Out[16]//FullForm=
Power[2, Rational[1, 2]]

In[17]:= FullForm[Sqrt[2] // Print]
$\sqrt{2}$

Out[17]//FullForm=
NullYou have to instead use in the For loop

\[Lambda] = Catenate[{\[Lambda], {\[CapitalLambda]}}]; Print[\[Lambda]]

 

[member 428835]

Thanks all! I would have replied a while ago but for some reason I did not receive email notifications. I have it working!