@Carl Love 

That is really very strange. For me, it said update available. 

I was also running 2023.2 before.

The update went smooth like always. Other than the version number not changing.

@Carl Love 

Why download the update?  The way I always update is like this:

Open Maple and do

                   Tools->Check for Update

If there is an update, it will say so. Then clicked Update.  At one point it will ask you to close Maple in order to finish the update. After closing Maple, it will now finish. 

Now open Maple, and check the version, it should say the new version.

But in this case, the version number was not changed. Which is why I asked above. It should have changed.

windows 10.

I just installed the update. When I start Maple again it still says  2023.2 

I was expecting it to say 2023.2.1

How does one know for sure they are running 2023.2.1 if the version number still says 2023.2? Is there a different command than the above to use that will display 2023.2.1 ?

interface(version)
    Standard Worksheet Interface, Maple 2023.2, Windows 10, 

       November 24 2023 Build ID 1762575


version()
 User Interface: 1762575
         Kernel: 1762575
        Library: 1762575

                            1762575

How did you generate the bode plot? You need transfer function to generate bode plot?

restart: 
alias(DS=DynamicSystems): 
sys:=DS:-TransferFunction(5*s/(s^2+4*s+25)): 
DS:-BodePlot(sys,output=dualaxis, range=0.1..100);

so you already has the TS. Even if you have state space, you can convert that to TF.

how to find CharacteristicPolynomiall of matrix with vector entries?

I do not understand what the issue is. Why not just do something like

V1:=Vector[column]([1,2,3]);
V2:=Vector[column]([4,7,9]);
V3:=Vector[column]([99,8,11]);
M:=Matrix([V1,V2,V3]);
LinearAlgebra:-CharacteristicPolynomial(M,x)

It works for me on Maple 2023.2

@Christian Wolinski 

I am interested to learn how  then you interpret the help page saying

    "It will do the simultaneous substitutions specified by the eqi equation arguments in the last argument expr"

Would that not imply all substitutions are done in place and at same time on the original expression? This is how I read it.

Ofcourse, the help page could be wrong and internally it does as you described. I do not know.

@Carl Love 

opps, you are right. I forgot this rule. So maple's Math is the correct one.  I need to go have more coeffee.

@Christian Wolinski 

I thought that is what it did, this is why I asked if order matters. But that would be really wrong design if this was the case. Also help says

And dictionary says  that simultaneous means:  occurring, operating, or done at the same time.

So it should be doing the substitution in "batch mode", ie, at same time. Not do one. Evaluate the new expression, and now do the next replacement on the new expression, which ofcourse could now have changed, reshuffled, order of operands might change, number of operands changed, and so on. This design would make no sense from the user point of view if this was the case, right?

But who knows. May be help is wrong and may be it works as you said.

fyi, this gives zero

VectorCalculus:-Laplacian(1/r, 'spherical'[r,phi,theta] )

                         0

@Preben Alsholm 

Thanks. But I am little confused what is the bottom line here. Is this a bug in has?

But if one wants to write a function that takes in P, where P is the plot generated by DEplot, and return true of false depending if the plot is empty or not, then what will this function looks like based on what you found above?

@sursumCorda 

are all allowed

Not on V Maple 2023.2. The last fails.

I looked for this sometime ago, and could not find one. Yes, it will be nice to be able to do the same as Matlab. But nothing like ~ exist in Maple as far as I know.

@Carl Love 

Thanks. That is good to know. I had no idea that subs will do it, as I use eval() all the time to replace symbols in expression.

It seems because subs does not do evaluation it worked in this case. It is really hard sometimes to figure out when to use eval and when to use subs when one wants to replace things in an expression. But in this example, will use subs then.

@Carl Love 

Yes, I understand why it failed when using curved. I knew it is because it did something different that when the arrow is not curved.

But this is really beside the point. These are internal detailes the user of the software should not care about.

When I write a function that takes two options, and it fails when using option 1 but does not fail when using option 2, then this  is a fault of my function. Not the user for using wrong input.

Software should be robust and not fail like this. For example, if Maple is not able to do it internally using curve arrow for some cases, it should internally handle this. May be not process the curve at that location and leave it empty and go on to the next location. Or may be do something else.

But it should not give an exception.  

@Carl Love 

Please see what I wrote above about it failng ONLY when using 'arrows'='curve'. My code works fine using y = -1.6 .. 1.6 when not using the option arrows = 'curve'. That is the whole point of what I am asking.

restart;
ode := diff(y(x), x) - 1/(-x^2 + 1)^(1/2) = 0;
x_range := -0.99 .. 0.99;
DEtools:-DEplot(ode, y(x), x = x_range, y = -1.6 .. 1.6, [y(0) = 0]);

works fine.

restart;
ode := diff(y(x), x) - 1/(-x^2 + 1)^(1/2) = 0;
x_range := -0.99 .. 0.99;
DEtools:-DEplot(ode, y(x), x = x_range, y = -1.6 .. 1.6, [y(0) = 0],arrows = 'curve');

error

So I expect the software to not fail when using arrows = 'curve'