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These are questions asked by mmcdara


This chunk of code gives me almost instantly the desired result with Maple 2015 but fails returning a result after 5 minutes when ran from  Maple 2020.
Changing the method or trying to tune their options doesn't fix the issue (for a larger value of the absolute tolerance the result, close to 1, is even obviously false).

Could you please help me to fix this?



`Standard Worksheet Interface, Maple 2015.2, Mac OS X, December 21 2015 Build ID 1097895`



Model_1 := (X, Y, Z) -> 1.3479120558270161+(-1)*.3390713110446567*X+1.0332964944900824*Y+(-1)*.8046331250569234*Z+0.9028899142595827e-1*X^2+(-1)*.28022910356641223*Y^2+1.3698461513469624*Z^2+0.6023630210658247e-1*Y*X+(-1)*.1988111077193626*Z*X+.6782902277463169*Z*Y+(-1)*0.7589729001497135e-1*X*Y*Z:

Model_2 := (X, Y, Z) -> .7215754021067852-.961682838202105*X+.4890842364596477*Y-.8214961524335734*Z+.15745942215497866*X^2-1.8023544416693338*Y^2+.36598799463016246*Z^2+1.3957614823018496*Y*X+.725398415577742*Z*X+1.9474707393604542*Z*Y-1.1780201448596594*X*Y*Z:

ExpMod_2 := unapply(expand(Model_2(Model_1(X1, Y1, Z1), Y2, Z2)), (X1, Y1, Z1, Y2, Z2)):

fy1 := PDF(Normal(0.1055, 0.0297), Y1):
fz1 := PDF(Normal(1, 0.2/3), Z1):
fy2 := PDF(Normal(0.17, 0.0476), Y2):
fz2 := PDF(Normal(1, 0.2/3), Z2):

C   := evalf(
         (1-eval(CDF(Normal(0.1055, 0.0297), Y), Y=0))
         (1-eval(CDF(Normal(0.17, 0.0476), Y), Y=0))
         (eval(CDF(Normal(1, 0.2/3), Z), Z=1.2)-eval(CDF(Normal(1, 0.2/3), Z), Z=0.8))^2

J  := Int(
        fy1*fz1*fy2*fz2*(1+tanh(10^4*(ExpMod_2(2.14, Y1, Z1, Y2, Z2)-1.25)))/2,
        method = _CubaDivonne, methodoptions=[absepsilon=1e-8]

Prob(X__2 > 1.25) = nprintf("%1.3e", evalf(J)/C);

Prob(1.25 < X__2) = `8.462e-08`




A question by @Shameera  I was working on has disapeared meanwhile.
It was related to this previous thread 233822-How--To-Solve-This-Equation-By-Using but has not been displaced in it.
Did a regolaror do this or was it  @Shameera ?

When using the Statistics package to declare a variable, let's say A,  as random, this variable is associated (assigned?) to a variable of name _R or _Rn with n a non-negative integer.
Subsequently, each expression you construct that contains the name A is displayed in a form where A has been replaced by its "alias" name _Rn.
Here is an example

A := RandomVariable(Uniform(0, 1)):
B := RandomVariable(Uniform(0, 2)):
C := RandomVariable(Uniform(1, 2)):
F :=  (A+2*B)/C
                          _R + 2 _R0

Is it possible,  to display F under its original form?
Is it possible to recover that _R is in fact A, that _R0 is in fact B and so on?

Maple (2015) fails to instanciate a Matrix with a list of elements of type string
(for instance Matrix(2, 2, ["A", "B", "C", "D"]) )

Matrix(2$2, [1$4]):    # ok
Matrix(2$2, [A$4]):    # ok

Matrix(2$2, ["A"$4]);  # not correctly understood by Maple (2015) 
Error, (in Matrix) initializer defines more columns (4) than column dimension parameter specifies (2)

Is this a bug?
Maybe something corrected in earlier versions?

I solve numerically a DAE system whose independent variable is named t and the dependent variables are d[1](t), ..., d[n](t).
I would like to to 2D or 3D plots of the solutions and color the resulting curve using a function f(...) of the remaining dependent variables.

Here is a simple example.





sys := {
   diff(x(t), t) = v(t)
  ,diff(v(t), t) = cos(t)
  ,x(0) = -1
  ,v(0) = 0

  ,px(t) = piecewise(x(t) >=0, 1, -1)
  ,pv(t) = piecewise(v(t) >=0, 1, -1)

sol := dsolve(sys, numeric):


odeplot(sol, [t, x(t), v(t)], t=0..4*Pi)


# I would like to color this space curve depending on the signs of x(t) and y(t)
# for instance, f being a "color function"
f := proc(s)
  local a, b:
  if s::numeric then
    a := round(eval(px(t), sol(s))):
    b := round(eval(pv(t), sol(s))):
    return piecewise(a+b = 2, "Green", a = 1, "Red", b = 1, "Blue", "Gold")
  end if:
end proc:

SOL := proc(s)
  if s::numeric then
    eval([t, x(t), v(t)], sol(s))
  end if:
end proc:

# I would like to make something like this to work

plot3d(SOL(s), s=0..4*Pi, colorfunc=f(s)):  #... which generates a void plot


# In some sense a continuous version of this

opts := symbol=solidbox, symbolsize=20:
display( seq(pointplot3d({SOL(s)}, opts, color=f(s)), s in [seq](0..6, 0.1)) );




How can I fix (if possible) the syntax in the command 

plot3d(SOL(s), s=0..4*Pi, colorfunc=f(s)):


Thanks in advance

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