I'm trying to get the plot command to display correctly on a logarithmic axis. The calculations in Maple are correct but the plots using logarithmic axis are wrong and start at different points on the x-axis. Is there a way to force Maple to display set points along the axis? e.g. 1, 3, 5, 10 of each logarithmic range. 

Log_plot_example.mw

When running this

expr:=5;
for item in expr do
    print(item);
od;

it prints 5 as expected. When when running

expr:=I;  (* NOTICE this is complex  I not the number 1 *)
for item in expr do
    print(item);
od;

it prints the number 1 and not I

I am sure there is a good reason why this happens.

But what should one do to insure they get the complex I in the second example when iterating over a sum of numbers, which in this example happened to be just one number who is complex? I know I can add explicit check to avoid this edge case.

The problem is that I want to iterate of sum of iterms, One or more of them can be complex I. (it is a result of doing series expansion of function at infinity, and I want to iterate over each term in the series one by one).

expr:=9+I:
for item in expr do
    print(item);
od;

Gives   9,1   and not 9,I

While

expr:=a+I:
for item in expr do
    print(item);
od;

does now give exected output   I,a  and not 1,a

What should one do to insure the for loop always get each term in the sum, even if it is complex?

I can't check the item inside the loop, because by then it is too late as the compelx I is lost already.

Is there a better way to iterate over sum of terms and look at each term as is and not lose the complex I in the way?

Maple 2022.1

Update 

For now, I am doing this hack. Since the input is always a sum (with + or - terms), then I convert the input to string, split on delimitors and then parse the entries back to Maple and now it is a list so I can iterate over each term. 

expr:=I+3:
String(expr):
StringTools:-SubstituteAll(%,"+","|+"):
StringTools:-SubstituteAll(%,"-","|-"):
StringTools:-Split(%,"|"):
map(Z->parse(Z),%):
for item in % do
    print(item);
od;

And when expr is

expr:=1+5*I+sin(x)-sqrt(8)*I-a;

It is a hack, but I could not find a relaible way to iterate over each term in the sum of terms without losing the complex I if one term was complex. I need to test this more. It is meant to work only on expression which is sum of terms, which is where I will use it.

Compare the output of the above for expr:=1-I;

The for loop gives 1,-1  but the string hack gives 1,-I which is what I wanted.

Ofcourse the above could fail if there is a "-" or "+" inside the term itself (for example  1+I+sin(1-x) , but this do not happen for the cases I am using this for, which just looking at terms of series expansion around either zero or infinity. These will be just power series terms separated by "+" or possibly "-"

If there is better way do this, that will be great.

Given a module A, it has a proc which is called to set some internal variable to some value. This proc is meant to be used as initialization of the module, and not meant to return anything (i.e. procedure vs. a function in other languages, where a procedure does not return anything, but a function does).

When this proc is called from outside, the result of the last assignment in the proc is returned back to the user since that is the default behavior.

Is there a way to prevent this, other than adding an explicit NULL at the end of this proc?  Adding : at the end the last statement or at the end of the proc did not prevent this.

Here is an example

restart;
A:=module()
  local r::integer;
  export set_r:=proc(r::integer)   
    A:-r:= r:   
  end proc:
end module:

Now when calling  A:-set_r(10), Maple will return back/echo back 10. But this is not something I want.

A:-set_r(10);

    10

To prevent this, currently I add NULL; at end of the proc, like this

A:=module()
  local r::integer;
  export set_r:=proc(r::integer)   
    A:-r:= r:   
    NULL;
  end proc:
end module:

and now

A:-set_r(10);

returns nothing. Well, it returns NULL but that is like nothing.

My question is, is there a better way to do this? Can one define a proc in Maple that returns nothing?

Maple 2022.1

I want to replace   expression that contains function whose first argument is always R0 with r0.

I can do it when the function is  f(R0) or f(R0,x) but I do not know how to tell Maple to do the replacement of the first argument, if the function has 0 or more arguments beyond R0.  This is what I tried

Download oct_11_2022_anyfunc.mw

I do not want to keep writing anything,anything,anything, for as many times as there could be more arguments.  I wan to say something like

evalindets(expr, 'anyfunc(identical(R0),anything_zero_or_more_arguments)', Z-> subsop(1 = r0, Z ));

Is there a better way to do this whole thing than what I am doing?

Update

Just after I posted this question, I found another structured type that worked

expr:=A+f(R0,x,y,z,h);
evalindets(expr, 'patfunc(identical(R0),anything)', Z-> subsop(1 = r0, Z ));

So patfunc works for zero or more argument after R0, which is what I wanted.

Given that types are core part of Maple, I find it so amazing that the help page "Definition of a Structured Type in Maple"  has so little examples and description of all these types in it. I can't figure what 80% of the types there do, since there are no examples.

Maplesoft should really do a better job on this page and add much much more examples and description. After all, strong typing is what is supposed to be the strength of Maple. But looking at this help page, it does not give one this impression at all.

I have a matrix and generate difference tables from it's diagonals. Works fine. Then I make a polynomial from the first row of the difference table. I have three polynomials. They are all acting inert, just will not evaluate.

I cannot see what the problem is.
 

Download Q_10-10-22_gentrate_eqn.mw

Hi,

I have developed a series of two dimension PDE equations (x,t) and I am going to solve them numerically in Maple. 

However, after putting all equations, initial conditions and boundary conditions, I faced couple of errors. I would be grateful if you kindly look at the code and let me know how I can solve it.

Thank you

Here is the code:

restart: with(plots): with(LinearAlgebra):

L:=0.003:   # thickness
rho_w:=997.77:
rho_s:=1419:
lambda_s:=0.46:
lambda_w:=0.644:
lambda_g:=0.026:
cp_s:=3734:
cp_w:=4183:
cp_v:=1900:
cp_a:=1005.68:
M_v:=18.016:
M_a:=28.966:
R:=8.314:
epsilon:= t -> 0.9*(1-t/10):
Cw0:=6:
Sw0:= Cw0/rho_w/epsilon(0):
pi:=3.1415:
p0:=patm:
patm:=10^5:
T0:=256:
p_air:=0.2*19724:
h_m:=0.017904:
h_T:=16.746:
T_air:=380:

Xdb:= (x,t) -> S(x,t):
Cw:= (x,t) ->  rho_w*epsilon(t)*S(x,t):  
Cg:= (x,t) -> rho_g(x,t)*epsilon(t)*(1-S(x,t)):
Cv:= (x,t) -> rho_v(x,t)*epsilon(t)*(1-S(x,t)):
Ca:= (x,t) -> rho_a(x,t)*epsilon(t)*(1-S(x,t)):
nw:= (x,t) -> -rho_w* k_rw(x,t)*K(t)/(mu_w(x,t))*(diff(p(x,t),x)-D_c(x,t)*diff(Cw(x,t),x) ):
ng:= (x,t) -> -rho_g(x,t)* k_rg(x,t)*K(t)/(mu_g(x,t))*(diff(p(x,t),x)):
nv:= (x,t) -> -w_v(x,t)*rho_g(x,t)* k_rg(x,t)*K(t)/(mu_g(x,t))*(diff(p(x,t),x))-binary(x,t):
na:= (x,t) -> -(1-w_v(x,t))*rho_g(x,t)* k_rg(x,t)*K(t)/(mu_g(x,t))*(diff(p(x,t),x))+binary(x,t):
M_g:= (x,t) -> M_v*w_v(x,t)+M_a*(1-w_v(x,t)):
rho_g:= (x,t) -> p(x,t)*M_g(x,t)/R/T(x,t):
rho_v:= (x,t) -> rho_g(x,t)*w_v(x,t):
rho_a:= (x,t) -> rho_g(x,t)*(1-w_v(x,t)):
binary:= (x,t) -> rho_g(x,t)*epsilon(t)*(1-S(x,t))*Deff(x,t)*diff(w_v(x,t),x):
Deff:= (x,t) -> 2.3*10^(-5)*p0/p(x,t)*(T(x,t)/T0)^1.81*(epsilon(t)*(1-S(x,t)))^(4/3):
mu_w:= (x,t) -> rho_w*exp(-19.143+1540/T(x,t)):
mu_g:= (x,t) -> 0.017/1000*(T(x,t)/273)^0.65:
p_veq:= (x,t) -> p_vsat(x,t)*a_w(x,t):
p_vsat:= (x,t) -> exp(-5800.2206/T(x,t)+1.3915-0.0486*T(x,t)+0.4176*10^(-4)*T^2-0.01445*10^(-7)*T^3+6.656*ln(T(x,t))):
a_w:= (x,t) -> exp(-0.182*Xdb(x,t)^(-0.696)+0.232*exp(-43.949*Xdb(x,t))*Xdb(x,t)^0.0411*ln(p_vsat(x,t))):
h_fg:= (x,t) -> 3167.2-2.432*T(x,t):
I_vap:= (x,t) -> M_v*K_eff*(p_veq(x,t)-p(x,t))/R/T(x,t):
K_eff:=1000:
rhocp:= (x,t) -> w_v(x,t)*epsilon(t)*(1-S(x,t))*rho_g(x,t)*cp_v+(1-w_v(x,t))*epsilon(t)*(1-S(x,t))*rho_g(x,t)*cp_a+epsilon(t)*S(x,t)*rho_w*cp_w+(1-epsilon(t))*rho_s*cp_s:
lambda:= (x,t) -> epsilon(t)*(1-S(x,t))*lambda_g+epsilon(t)*S(x,t)*lambda_w+(1-epsilon(t))*lambda_s:
ncp:= (x,t) -> nv(x,t)*cp_v+na(x,t)*cp_a+nw(x,t)*cp_w:
k_rw:= (x,t) -> S(x,t)^3:
k_rg:= (x,t) -> 1.01*exp(-10.86*S(x,t) ):
K:= t -> 10^(-10)*(1-t/10):
D_c:= (x,t) -> 10^(-8)*exp(-2.8+2*Xdb(x,t)):

PDE_m1:=diff(Cw(x,t),t)+ diff(nw(x,t),x)=-I_vap(x,t) :
PDE_m2:=diff(Ca(x,t),t)+ diff(na(x,t),x)=0 :
PDE_m3:=diff(Cg(x,t),t)+ diff(ng(x,t),x)=I_vap(x,t) :
PDE_T:=diff(rhocp(x,t),t)+ diff(ncp(x,t)*T(x,t),x)=diff( lambda(x,t)*diff(T(x,t),x),x) -h_fg(x,t)*I_vap(x,t):

IBC_S:={S(x,0)=Sw0, D[1](Cw)(0,t)=0, subs(x=L,nw(x,t))=epsilon(t)*S(L,t)*h_m/R/T(L,t)*(p_veq(L,t)-p_air) }:
IBC_p:={D[1](p)(0,t)=0,p(L,t)=patm,p(x,0)=patm}:
IBC_T:={h_T*(T(L,t)-T_air)+epsilon(t)*S(L,t)*h_m/R/T(L,t)*(p_veq(L,t)-p_air)*h_fg(L,t)=0, T(x,0)=T_air, D[1](T)(0,t)=0}:
IBC_w:={w_v(x,0)=0.0262, subs(x=L,nv(x,t))=epsilon(t)*(1-S(L,t))*h_m/R/T(L,t)*(p_veq(L,t)-p_air), D[1](w_v)(0,t)=0 }:

pds:=pdsolve(PDE_m1,PDE_m2,PDE_m3,PDE_T,{IBC_S,IBC_p,IBC_T,IBC_w},numeric);
 

mint gives messages such as

 These local variables were assigned a value, but otherwise unused:  i

even though it does say what proc this is in, it does not give the line number where such problem is at.

So if a proc is long, say 100 or 200 lines, it is very hard to find the location of such things visually all the time.  Searching for "i" is not too useful.

Tried different options but there are no line numbers given for these messages.

"C:\Program Files\Maple 2022\bin.X86_64_WINDOWS\mint.exe" -i 2  foo.mpl

Using  -i 4 gives much more information, but no line numbers.

Are there other things to try? I think mint should be improved and list line number for each warning and message such as also These local variables were assigned a value, but otherwise unused: 

It should give lines numbers where this happened to make it easier to locate in the editor.

Maple 2022.1 windows 10.

How can one ask Maple 2022 to give the non-trivial solution to this differential equation 

V’(t)=-2*V(t)^(2/3) with V(5)=0 ?? 

Have tried dsolve({V’(t)=-2*V(t)^(2/3),V(5)=0}). But that only gives me the trivial solution V(t)=0.

Do you think the following messages  by mint should have been the same? this is just some made up example with no purpose other than to show the messages.

foo:=proc(x)
local z,a:=1,la;
   patmatch(x,a*x,'la');   
   map(z->assign(z),la);
end proc;

boo:=proc(y,x)
local Z,RHS;   
   RHS:=y(x);
   subs(y(x)=Z,RHS);
end proc;

Looking at the above, foo() has z used but never assigned a value, right?  And in boo(), Z is used but never assigned a value.

but mint gives slighlty different message

"C:\Program Files\Maple 2022\bin.X86_64_WINDOWS\mint.exe" -i 2  A.mpl

Procedure foo( x ) on lines 2 to 6
  These local variables were never used:  z

Procedure boo( y, x ) on lines 8 to 12
  These local variables were used but never assigned a value:  Z

Should not these two messages have been the same?

When running mint on a single .mpl file, I often get this warning

These names were used as global names but were not declared:  main_module

When having this code in the mpl file

o:=Object(main_module:-person_type);

The problem is that main_module is a module that lives in separate mpl file.

It is a differerent module in its own ,mpl file which inside it contains the person_type definition. (another module of type object)

I know I can ignore this. And have been. But my question is: how does one "declare" main_module inside this mpl file to avoid getting this warning message? Since main_module is its own module in separate file. I do not understand what does it mean to  "declare" it.

Here is the full code

A:=module()
   export boo:=proc()
      local o;
      o:=Object(main_module:-person_type);
      o:-foo();
   end proc;
end module;

And here is the command I used

"C:\Program Files\Maple 2022\bin.X86_64_WINDOWS\mint.exe" -i 2 A.mpl

Gives

Nested Procedure boo() on lines 2 to 6
  These names were used as global names but were not declared:  main_module

Later on, when I build my .mla library, all these modules are put inside the library. So it is not an issue when running the code, but I'd like to see if it is possible to add something to A.mpl to tell Maple that main_module is separate module and not to worry about it.

I have started to use CodeGeneration[C] instead of codegen[C] (depreciated). In the attached example not all variables and parameters of a C function are declared as double, although the default value is double.

If this is by design:

How can I force double without going back to codegen[C] or manual declaration of each item?

C_code_generation_with_CodeGeneration.mw

again, I wish Maple help can be better. A simple example of how to use listplot on matrix is all what is needed.

I have a matrix, 3 rows and 5 columns. I need to use listplot to generate 3 listplots on same graph. I can do this one row at a time. But when calling listplot(m) where m is the matrix, it gives error

Error, (in plots:-pointplot) incorrect number of coordinates in points data

Clicking on the above link, as usual sends me to page that says There is no help page available for this error

Help says

The listplot command also accepts a list or Matrix containing points data. great. But how?? I click on the link next to the above line, it sends me to page about pointplot. There is says that pointplot also accepts a matrix of size n by 2. Does this mean listplot matrix must also be two columns? It does not say this on the listplot help page.

For a workaround, I now generate plot of each row on its own, then use display to put them all on same graph. But the problem with this is that all have same color. I was hoping that if Maple did it all at once, it will automatically pick different color for each line as is the case with Mathematica (example below)

Is there a better way to do this? For reference, I'd like to generate similar plot like this

You see, the colors are automatically selected. With manual plotting of each row myself, I have to select the color myself and to make sure they are different and so on. It will be better if the system did all of this.

Please see attached worksheet

Download how_to_list_plot_matrix.mw

What is the correct way to use listplot with matrix?

I am not able to even trap this Maple exception.

Any suggestions what to do? It is not a problem if it can't solve it, but I need to at least be able to  trap the exception in order to go to the next one, else the whole program now stops when it hits this.

I used try..catch but this exception just ignores this and escapes to top level. This is not the first time I've seen Maple exception escape the try/catch. I do not understand why some do that and some not. I

Is this another bug?

Download how_to_trap.mw

Hello,

I don't understand. With 2 degrees of liberty and a factor of 5% (1-95%), the table Khi-2 indicates 5,99.

It is impossible for me to obtain this value with Mapple. 2 following tests :

Y := ChiSquareRandomVariable(2);
                            Y := _R0

PDF(Y, 0.05);
CDF(Y, 0.05);
                          0.4876549560

                       0.0246900878919645

PDF(Y, 0.95);
CDF(Y, 0.95);
                          0.3109425282

                       0.378114901350325

The same problème with the instruction RandomVariable(ChiSquare(v)).

Thank you to help me.

Kinds regards