There appears to be a bug with Maple 2023.2 which will remove units from physical constants.

AddConstant(Solar_equatorial_radius, symbol = r[e,Sol], value = 696342., uncertainty = 65., units = km) :

AddConstant(Solar_flattening, symbol = f[Sol], value = 0.000009) :

AddConstant(Solar_polar_radius, symbol = r[p,Sol], derive = -r[e,Sol]*(f[Sol] - 1)) :

AddConstant(Solar_nonradius, symbol = x[Sol], derive = f[Sol]*r[e,Sol]) :

In the example here, "GetUnit(Constant(r[p,Sol]))" will return "1" and "GetUnit(Constant(x[Sol]))" will return "m".

The only workaround is to not save dimensionless quantities as physical constants or otherwise at least some constants derived from a dimensionless constant will also be dimensionless.

Adding "units = 1" to "AddConstant" does not help.

Hello! We are using Maple to evaluate numerically expressions with very high precision and we are finding very strange results. After some playing with simple models we have come to conclusion that there might be a bug in Maple 2023. Here is a clean example of what we are experiencing. Plotting the function x*exp(-x) in [0,20]. Clearly the function cannot be negative in that interval! However, if Digits is set to 40 the results may be whatever. Any ideas? Thank you very much. 

Trying to figure out how to save a slice of an array to a repository.

for example: savelib(vmcofs[1],lib) [where lib is my repository location]

I'm getting the error: Error, invalid input: savelib expects its 1st argument, to be of type symbol, but received vmcofs[1]

Quoting it doesn't seem to help.

I need to do this programmatically as I will be incremented the row number in the array and saving partial data at each step.

That is...savelib(vmcofs[1],lib) then savelib(vmcofs[2],lib), etc.

I can save the whole array. Is there a more efficient way of doing this?

Hello everyone!

I'm using Maple 18. The problem is that fsolve does not solve equations, or more precisely, it does not pass the values of sU - from its range, and sV - from its range, to shootNL. As a result, R value:=[]; . I would like to ask for help in solving this problem.

I have attached the Maple source file.

fsolveProblem.mw

I want to plot a graph of sets of o d e for a disease model with varying perimeters please how do I get the plot functions and how should the graphs look like for each parameter I vary

I'm interested in created a group ring, but have no idea how to do it.

In short, a group ring is a free module with the scalars as elements of a ring,R, and the vectors as elements in a group, G. [Wikipedia has a decent description.]

Elements a=r0*g0 and b=r1*g1 have sum a+b=r0*g0+r1*g1 and product a*b=r0*r1*g0*g1

The distributive property is followed.

Suggestions?

Is there a way to remove a unit symbol?  "AddUnit" allows to add additional symbols or change the default symbol, but I don't see any way to remove symbols?

A good example is for the hectare.  Maple 2023 uses "a" as the default symbol for the are, except that the unit symbol "a" does not allow using SI prefixes because the peta- unit prefix then conflicts with the pascal ("Pa").  I can use "AddUnit" to change the default symbol for the are from "a" to "are" but I still cannot enable SI prefixes unless the symbol "a" is removed from the symbol set.  This way hectares ("hare") and petares ("Pare") can be used.

I don't see a way to nondestructively/temporarily delete units either ("RemoveUnit").  Deleting the unit "are" and then recreating it as a new unit with the symbol "are" would solve the same problem.

I just saw that there already exists a separate "hectare" unit with the symbol "ha" which presumably also needs to be removed in order to enable SI prefixes for "are".  This is just one example but a general way to remove units and/or unit symbols should be very helpful.

I'm an engineer and when showing results of calculations, some values will display as fractions, and I would prefer that instead floating numbers are displayed.  Also, there is kind of a quirk where if the multiplier of a unit is 1, the result displays as a unit only. I would prefer to see 1*A rather than A.

I wrote this simple proc to convert a value with or without attached unit to a floating point number if it is a fraction or if it has a unit and the coefficient is 1.

Let me know if there is a more elegant way to do this or you have any suggestions or questions.

   unrationalize := proc(x)
        local 
            returnval,
            localcoeff,
            localunit
        ;
        description
            "Converts a fractional number to float",
            "Units are supported"
        ;
        if type(x, fraction) or type(x, with_unit(fraction)) then 
            returnval := evalf(x)
        elif type(x, with_unit(1, 'localcoeff', 'localunit')) then
            returnval :=  evalf(localcoeff)*localunit
        else 
            returnval := x;
        end if;
        return returnval;
    end  proc;
# Testing the proc
list1 := [1/2, 1/2*Unit(('A')/('V')), 1, Unit('A')];
listDescription := ["Fraction", "Fraction with Unit", "Unity", "Unity with Unit"];
for i, myValue in list1 do
    [listDescription[i], "evalf:", evalf(myValue), "unrationalize:", unrationalize(myValue)];
end do;

hi i need help. can someone help me with maple command for this 2 question? i need to do it for my assignment. all i know that i need to use with(vectorcalculus). all command include graph. thanks

In case this error has been corrected in more recent versions, please feel free to delete this question.

In the felp page relative to anames this example is given

restart:
test1 := 1: test2 := 2: test3 := 3.2: testall := 3.2:
select(type,{anames()},suffixed(`test`));
                 {test1, test2, test3, testall}

Note the backward quotes in suffixed(`test`).
This works only if test is not an assigned name itself:

restart:
test := 0: test1 := 1: test2 := 2: test3 := 3.2: testall := 3.2:
select(type,{anames()},suffixed(`test`));
Error, (in type/suffixed) expecting a 1st argument of type {string, symbol, list(symbol, string), set(symbol, string)}

With simple quotes:

select(type,{anames()},suffixed('test'));
              {test, test1, test2, test3, testall}

Hi,

I am exploring the counting functions available in Maple, and I am searching for how to enumerate arrangements with repetition and combinations with repetition ? ThanksCombinatoireTEST.mw

How to handle these errors in plotting the solutions?compare.mw

Currently, the argument is mapped to the HUE coloring scheme (I guess)

plots:-complexplot3d(z, z = -2 - 2*I .. 2 + 2*I, title = -ln(1/c) - ln(c), orientation = [-90, 0, 0])

This makes it difficult to distinguish the sign of the argument close to the positive real axis (just to give an example). To increase contrast I thought about alternatives: Linear ramping from 0 to 2pi from one color to another (similar to phase wrapped images) or a stepped color scheme (in pi/4 increments for example).

I tried color=argument(z/2/Pi) but this did work.

Is there a way to import an MPL file from a URL?

Import("https://www.nicolesharp.net/testbox/test.mpl");

Using the "Import" command on Maple 2023.2 appears to only import the MPL as plaintext and doesn't recognize any of the Maple instructions from the MPL file.

Using the "Get" command with the URL package doesn't do anything useful either.

with(URL) : Get("https://www.nicolesharp.net/testbox/test.mpl");

I recently stumbled across this video Why do calculators get this wrong

At some point, the author (Matt Parker) mentions the Farey's algorithm as a way to get a rational approximation of a number between 0 and 1.
Just for fun I applied this algorithm to build increasingly accurate rational approximations of Pi (see here Rational_approximation.mw). 
The rational approximation 

convert(evalf(Pi), rational);
                             104348
                             ------
                             33215 

is one of those the Farley's algorithm returns.

Is this pure chance, or does Maple indeed use the Farley's algorithm?
If not, what algorithm does convert/rational use?