## 564 Reputation

16 years, 242 days

## Is there a way to do this?...

Is there a way to do this?

Thanks!

## Thanks alot! this command...

Thanks alot!

this command works for me:

plot( Re(subs(deltaE=0.355,M=sqrt(5.4e5),Eig1(R^(1/3)))),      R=1..10,labels=[R^3,'Eig1'(R)]);

although not when I have what you posted:

plot( Re(subs(deltaE=0.355,M=sqrt(5.4e5),Eig1(t^(1/3)))),      t=1..10,labels=[R^3,'Eig1'(R)]);

(with a t instead of an R) , it doesn't work for some reason.  Is it supposed to?

## Actually...

Actually, it would be even better if I could plot a function of x vs 9x^2

## That doesn't work, When I...

That doesn't work,

When I do

```> plot( Re(subs(deltaE=0.355,M=sqrt(5.4e5),Eig1(R))),
>       R=1..10^(1/3)

Maple returns the correct plot,

When I change " Eig1(R) to Eig1(t) " , without changing "R =1..10^(1/3)", I get the same result.

But when I change "R =1..10^(1/3)" to "t=1..10^(1/3)" I get an error message.

Also, I'm not sure if that would give me the output I want,
because if I plot x^2 vs x I should get a parabola ,
and if I plot x^2 vs x^2 I should get a straight line,
so the shape actually changes as well, and it's not just a matter of labeling.

Is there a way I can plot a function of x vs x^2 instead of vs x?```

## I mean, I can do plot(...

I mean, I can do

plot( Re(subs(deltaE=0.355,M=sqrt(5.4e5),Eig1(R^3))), R=1..10);

but ideally what I would like to be able to do is

plot( Re(subs(deltaE=0.355,M=sqrt(5.4e5),Eig1(R^3))), R^3=1^(1/3)..10^(1/3));

but Maple won't let me do that...  is there an alternative?

## Thanks a lot! I used the...

Thanks a lot!

I used the second command,

plot( Re(subs(deltaE=0.355,M=sqrt(5.4e5),Eig1(R))), R=1..10);

and it worked!

In your last line, you evaluated that limit to be 0 as R->infinity, although the plot shows that it goes to 0.355 (which is deltaE). And this is what I expected from theory as well.

I'm curious now as to how I could plot the same function against R^3 instead of vs R, without making a new variable equal to R^3 and redefining the function in terms of the new variable then plotting.  Any ideas???

## Thanks a lot acer!   That...

Thanks a lot acer!

That was very helpful.  I was not able to extract the elements of the eigenvalue vector  using

```a := evals[1]:

after getting the eingenvalues by
evals := LinearAlgebra:-Eigenvalues(M):

I tried on both Maple 10 and 11.  But I did the second thing you told me to do (right-clicking and using the context-menues, and then I was surely able to apply the commands
evals:=%; and a:=evals[1];

I'm not sure why a:=evals[1] didn't work when I got the eingenvalues the first way.
```

## Thanks acer, I have a matrix...

Thanks acer,

I have a matrix K,

and I got its eigenvalues by: eigs:= Eigenvalues(K);

Now I have the three eigenvalues in a vector called eigs.

I want to define Eig1:= "The first element of eigs" , Eig2 := "The second element of eigs" , Eig3:="the third element of eigs"

Without copying and pasting the expression originally given by Maple when I used the Eigenvalues(K) command.

My eigenvalues are gigantic and Maple's taking a LONG time to copy and paste them, and then it doesn't even paste them correctly, so I was hoping there was just a way to extract the n'th element of the vector eigs , just like in Matlab how we can do eigs(1).

## sorry I meant to include:...

sorry I meant to include: deltaE = 0.355

## Thanks!...

That's amazing, thanks a lot guys!! you were all VERY helpful!! =)

## Sorry, wrong question...

WOW..you guys are GREAT...i'm impressed with the speed and helpfulness of your responses. I actually realized that I asked the wrong question though.. What I have is a text file in VI, with two columns full of numbers, like: R1 R2 1..2.4 2..2.5 3..9.6 I want to create a 3rd and 4th column (R3 and R4), where R3=1/R1^2 and R4 = some complicated function of R2 and R1. Then I want to plot R4 vs R3! I am used to using Tecplot for Unix, and it reads my datafile perfectly and the 3rd and 4th columns are computed and plotted..but tecplot only keeps a certain number of digits when doing its computations, so my 4th column is not as accurate as I need. So I was wondering if Maple could read my datafile in the format that it's in and recognize the fact that there's two columns worth of information, and if I could do calculations on those columns. I tried writing a program in FORTRAN 77 to do these calculations, but although I'm fully familiar with the logic, I am having trouble with the programming language. I am aware of the fact that Excel can EASILY make the 3rd and 4th columns using the formula function, but I was wondering if Maple could do it as well. Thanks a lot guys!
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