Hello, 

I have come across a problem in Maple, when I try plotting af slope field from my differential equation. 

I have tried different ways of defining the ODE, but when I use it in the command of "linjeelementer" (Danish for line elements - It's a command that's part of a package called "With (Gym)" in Maple, it gives me the error: Error, (in DEtools/DEplot/CheckDE) - Derivatives must be given explicitly. 

I don't understand what derivatives I must "give explicitly"?

Translation of the relevant sentences if anyone needs it when looking at the screenshot:

"I need to draw a slope field for the differential equation along with the solution curve for the population growth in India after 1960.

I define the differential equation:
ODE := -0.000032229*y^2 + 0.065843*y - 15.103"

"I am drawing the slope field for the differential equation along with the solution curve for the population growth in India after 1960, i.e., the solution curve that passes through the point (0,449):I am drawing a slope field for the differential equation along with the solution curve for the population growth in India after 1960, i.e., the solution curve that passes through the point (0,449):
linjeelementer(ODE, y(t), t = 0 .. 350, y = 0 .. 2000)"

Hi,

I'm trying out the 2024 version of Maple and I'm getting the following warning message:

Warning, not a built-in function (`rtable_alias`)

which I didn´t get for the 2023 version. I have no clue where it is coming from since it happens even when I start a new worksheet:

I've also attached print outs of the same worksheets (from Maple help examples and from Maple Portal), one using Maple 2023 version and the other one using Maple 2024 version so youcould see the warning and some other problems.

I really appreciate if someone would have an idea of what is going on here. Thanks very much in advance.

interpolation_2023.pdf

interpolation_2024.pdf

optimization_2023.pdf

optimization_2024.pdf

This is perhaps a stupid question. It is quite easy to add a vector with minutes to 60 minutes. However, when I try to do this stating 1 hour instead of 60 minutes it does no longer do the calculation. Why is this? Thank you for any explanation.

QuestionMP.mw

In the example below, the second call to simplify is ineffective

eq := (a*x + b)/(c*x + d) = 1;

`simplify/nodenom`:= x -> (numer@(lhs - rhs) = 0)(x);                       
                      
`simplify/nodenom`(eq);
simplify(eq, nodenom);

Why is that?
Convert, for example, works

`convert/nodenom`:= x -> (numer@(lhs - rhs) = 0)(x);

`convert/nodenom`(eq);
               
convert(eq, nodenom);

Deal All,

I have a system of linear differential equations with unknown functions T[1](t) to T[n](t). In the attached example, I considered the value of n equal to 10, but depending on the problem, the value of n may be higher. Maple is not able to solve this problem analytically with the ‘dsolve’. 

Does anyone have an idea to analytically solve for such a set of linear differential equations?

Best wishes

Set_of_Linear_DEs.mw

I try to solve triple integraton in Maple with this code.

but it leaves the last integral dz in the answer and warns: unable to determine if a*h/(-b+a) is between 0 and h; try to use assumptions or use the AllSolutions option
What is the problem?
and i need to get V = Pi*h(a^2 + ab +b^2)/3

Regards

This is new:

Maple 2024 frozen on opening recent files

Maple 2023 frozen on opening

Maple 2022 frozen on opening start page

Maple 2021 blinking

Maple 2020 opening start page

The above system state is constant for about 30 min. Maple sessions without start page are working. I can enter code but file opeing and saving does not work. The fact that Maple 2020 is also not working makes it unlikely that the Java environement is part of the problem.

I have several times restarted the system. The rest of the system is working.

Something happened to the system and I have no clue what is was and what I can do about it.

Any ideas or suggestions what I could try? Windows 10.

Why Maple gives this error on solving first order linear ode using ODESteps? 

Download odesteps_fail_may_10_2024.mw

ps. also reported to Maplesoft customer support.

I want to rescale a projective vector. Have been using gcd on the numerators and denominators. This works in simple situations. It doesn;t work well here, admitadely the points have been just made up for the question.  Square roots seem to make it mal-preform. I run into a lot of squate roots in symbolic situations. What would be a better way? I have been wondering if frontend would help?

Download 2024-05-09_Q_Rescale_projective_vector.mw

I'm new to Mapple 2024, and probably miss something.
lie, e[i] i=1..4, and G are previously defined objects. Then whe I define:

cf:=(k,l,m,t,x,y,z)->seq(lie(p,e[k](t,x,y,z),e[l](t,x,y,z))*G(t,x,y,z)[p,m],p=1..4);
cf(2,4,2,t,x,y,z);

I get:

0, 0, 0, -6*(-6*z^3*(7*z - 4)*(z - 1)^2*(y^2 - 1)^3*(x^2 - 1)^2*x - 6*z^4*(1 - z)^3*(-x^2 + 1)^2*(-y^2 + 1)^3*x*(-3*z^2*(7*z - 4)*(z - 1)^2*(y^2 - 1)^3*(x^2 - 1)^3 - 7*z^3*(z - 1)^2*(y^2 - 1)^3*(x^2 - 1)^3 - 2*z^3*(7*z - 4)*(z - 1)*(y^2 - 1)^3*(x^2 - 1)^3) - (1 - z^3*(7*z - 4)*(z - 1)^2*(y^2 - 1)^3*(x^2 - 1)^3)*(-24*z^3*(1 - z)^3*(-x^2 + 1)^2*(-y^2 + 1)^3*x + 18*z^4*(1 - z)^2*(-x^2 + 1)^2*(-y^2 + 1)^3*x))*z^4*(1 - z)^3*(-x^2 + 1)^2*(-y^2 + 1)^3*x*(1 - z^3*(7*z - 4)*(z - 1)^2*(y^2 - 1)^3*(x^2 - 1)^3)

The 4th item eval as:
cf(2, 4, 2, t, x, y, z)[4] = -36*z^10*x^2*(x^2 - 1)^7*(7*z^2 - 8*z + 4)*(z - 1)^7*(y^2 - 1)^9*(-1 + z^3*(7*z - 4)*(z - 1)^2*(y^2 - 1)^3*(x^2 - 1)^3)

But when I define another function by just changing the seq operator with a sum operator:

cf2:=(k,l,m,t,x,y,z)->sum(lie(p,e[k](t,x,y,z),e[l](t,x,y,z))*G(t,x,y,z)[p,m],p=1..4);
cf2(2,4,2,t,x,y,z);

I get 0.

What do I miss ?

Good day to all of you nice people.
I'm currently attempting to plot a vector field where each component of the vector is defined by the equations S_x, S_y, and S_z, which are functions of the radial coordinate. Here is a depiction of how the vectors change with respect to r:

The next step, which I'm unsure how to do, is to plot the vectors around the z-direction, or I should say, in phi direction, to achieve something similar to this example:

Thank you a lot for your kind help. 

Here is my code:
Maple_Question.mw

In our recent project, we're diving deep into understanding the SIR model—a fundamental framework in epidemiology that helps us analyze how diseases spread through populations. The SIR model categorizes individuals into three groups: Susceptible (S), Infected (I), and Recovered (R). By tracking how people move through these categories, we can predict disease dynamics and evaluate interventions.

Key Points of the SIR Model:

• Susceptible (S): Individuals who can catch the disease.
• Infected (I): Those currently infected and capable of spreading the disease.
• Recovered (R): Individuals who have recovered and developed immunity.

Vaccination Impact: One of the critical interventions in disease control is vaccination, which moves individuals directly from the susceptible to the recovered group. This simple action reduces the number of people at risk, thereby lowering the overall spread of the disease.

We're experimenting with a simple model to understand how different vaccination rates can significantly alter the dynamics of an outbreak. By simulating scenarios with varying vaccination coverage, students can observe how herd immunity plays a crucial role in controlling diseases. Our goal is to make these abstract concepts clear and relatable through practical modeling exercises.

I have a complicated bivariate function f(Gamma,rho) that is a RootOf of a quartic. I know that it is strictly positive (one of the four roots at least) for Gamma=0..10 and rho in (-1,+1), with bounds excluded.

I need to find the signs of its first and second derivatives (wrt to Gamma and wrt to rho: 4 derivatives in total).

I encounter numerical issues when I plot3d the derivatives using D[]() vs. fdiff() (numerical function evaluations of the RootOf). I was hoping for the two commands to produce the same output, but they don't it seems. What's going on?

Script:

Download signs_derivatves_bivariate.mw

When I calculate the difference between two dates with the same day using the DateDifference Calendar function, I don't get an integer number of months, but results with extra days, hours, minutes, seconds and milliseconds. How can I calulate the actual number of months?

I appreciate any help.

Download DateDifference.mw

I never used Maple's StringTools:-RegSubs before.

I have a Latex string generated by Maple that has this form

"......    \\textrm{ ......   }  .... "

Where the dots mean anything, including space characters.  I need to change the part of the string  "\\textrm{ ...... }" to this

"......  \\begin{minipage}{\\linewidth}\\textrm{  ......   }\\end{minipage}  .... "

It is easy to change the opening part. Here is an example

s:="A& B& \\textrm{The fundamental matrix has } &C ";
s:=StringTools:-SubstituteAll(s,"\\textrm{","\\begin{minipage}{\\linewidth}\\textrm{");

Gives

The problem is how to replace the closing "}"  with "}\\end{minipage}".   I can't just replace "}" with "}\\end{minipage}" using SubstituteAll because I need to only change the "}" that closes the corresponding "\\textrm{" and not any other "}" that could be in the string.

So I need to use pattern matching or regular expression substitutions. The examples in help are not easy to understand.

Basically I need regular expression that matches 

                        "\\textrm{ WILDCARD * }" 

and change it to 

                        "\\begin{minipage}{\\linewidth}\\textrm{ WILDCARD * }\\end{minipage}" 

Any one know how to use Maple's egular expression to do this substitution using the above example?

Maple 2024 on windows 10.

Update

Thanks for the replies. I ended up writing small function that simply scan the string and do the replacement.