Hi everybody

I have two tables, namely A and B, the entries of wich can also be tables ... and so on.
These two tables have the same structure in the following sense :

Viewing A or B as tree graphs GA and GB :

1.  the set of the names of the vertices of GA is identical to the set of the names of the vertices of GB
2. GA and GB have the same connectivities

For instance A and B below share the same structure
A := table([x=table([u=1]), y=table([v=table([p=2]), w=3]) )]
B := table([ x=table([u=4]), y=table([v=table([p=12]), w=3]) )]

But not do A and C
C := table([x=table([u=1]), y=table(v=2, w=3]) )]

Let p(s) some path in GA from its root to some terminal leaf s.
B being "structurally identical" to A, GB also contains p(s)
Returning to the original tables, p(s) corresponds to a multi-index [k1][k2]...[kn] and the "value" of s is then given by A [k1][k2]...[kn]) or, symbolically A[p(s)]

I adopt this definition for "A = B" :
A is said to be equal to B iif the entry of A[p(s)] equals B[p(s)] for all the terminal leaves s
(here equals is intended in the "classical" senses, ie 3=3, {1,2}={2,1}, ...)
 

How can I check if "A=B" in the following sense ?

Thanks in advance

PS : Keeping in mind the analogy between A and GA, I have written a recursive procedure to check if A=B. But it is rather lengthy and I wondered if there could exist some Maple function to do this test ?


 

Hi everybody,

I solve an ODE system numerically with the command

Tend := ….. :
sol := dsolve(MySys, numeric, method=rosenbrock, range=0..Tend):    # or rkf45

One of my colleagues wants the solution in array form for using it in a spreadsheet (namely Excel). 
Here is an example of what I do :
 
data := plottools:-getdata( plots:-odeplot(sol, […..], 0..Tend, refine = Q) ):  # Q rational
result := data[3]:
ExcelTools:-Export (result, …)

To understand the following, you need to know that the time step varies by several decades (at least 3 or 4). and that  numfun is typically in the order of 10^5
 
When I ask Maple to construct  data , Maple seems to sample the solution solaccording to the local time step dsolve has selected (and probably some other parameters ?)
Because this time step varies in very large proportions, the result is sometimes a concentration of points in regions where the solution is rapidly changing (which is desirable) … with some lacunarity in slow varying regions.

To obviate this, sometimes  poor appearance, I used to force Maple to compute the solution by regularly sampling the range ]0, Tend[  and combining this array with the original one (result).
But this not satisfactory for I do not avoid lacunarity region (unless I proceed in some ad hoc way)

Here is my question :
Could you give me some elements about  the way odeplot adapts its sampling strategy according to the local time step, the budget N (the Q value I guess) and maybe numfun ?

Thank you in advance

Hello everyone,

Is it normal that commands #1 and #2 below do not return the same thing ?

L := [`Norman.Mailer`, `Richard.Brautigan`]

#1

map(u -> convert(u, string), L);

["Norman.Mailer", "Richard.Brautigan"]


#2

`convert/string`~(L)

["`Norman.Mailer`", "`Richard.Brautigan`"]


Side question : I am not really familiar with the tilde operator and I often use map instead.
Does it exist a better practice in these matters ?

Thanks in advance

Hi everybody,

I would like to understand why the instruction

seq(X__k, k=1..2)

returns

X_k, X_k

and not X₁, X₂ ?

Is it possible to force the evaluation of X__k each time k changes in the "seq" loop ?

Thank you for your explanations

Hi everybody,

This is a notional example.
I create a variable MyColor of type string, which contains some correct specification of a known color.
Two examples are
    MyColor := "CSS Red";            
    MyColor := "Resene LaRioja":

In the ColorTools package there exist a few couples of (a priori) reciprocal functions, for instance NameToRGB24 and RGB24ToName.
So I can expect that composing one of this function with its reciprocal is a neutral operation.

But, if I apply first  NameToRGB24 to a well formed MyColor color and next thits reciprocal RGB24ToName , I do not recover MyColor ... or at least not all the time


Example 1 : 
with(ColorTools):
MyColor := "CSS Red";    
RGB24ToName ( NameToRGB24 (MyColor) ); 
     "Red"

Let us observe the loss of the palette name ...


Example 2 : 
MyColor := "Resene LaRioja";    
NameToRGB24 (MyColor) ); 
      [179, 193, 16]
RGB24ToName ( % ); 
     error, (in ColorTools) unknown RGB color [179, 193, 16]


It seems that RGB24ToName ( NameToRGB24 (MyColor) ); works correctly only if MyColor refers to a color from palette CSS. This seems consisttent with the loss of the palette name in example 1 and the presence of the word RGB (and not RGB24) in this error message.
More generally, for colors from other palettes than CSS the same kind of error is returned (I did not do intensive testing ...)

Is this an error,
   or some limitation I missed,
      or an improper use of RGB24ToName ?

I look forward to your response