Questions - MaplePrimes

The plots:-fieldplot grid option can give a strang...

Asked by: jaytreiman 273

August 29 2019

0 2

I was playing with plots:-fieldplot in Maple 2019 and found that sometime the grid option gives a strange result. The code I used was

with(plots): fieldplot([-x/(x^2+y^2)^1.5,-y/(x^2+y^2)^1.5],x=-1..1,y=-1..1); fieldplot([-x/(x^2+y^2)^1.5,-y/(x^2+y^2)^1.5],x=-1..1,y=-1..1,grid=[8,8]); fieldplot([-x/(x^2+y^2)^1.5,-y/(x^2+y^2)^1.5],x=-1..1,y=-1..1,grid=[7,7]);

The first two plots come out as expected. The third plot has (0,0) in the grid, a point where the vector field does not exist. Rather than giving an error or ignoring the point, Maple 2019 (and 2018) plots a single arrow through the origin. The file with plots is below. I hope that this can be changed to give a different output.

>	with(plots): fieldplot([-x/(x^2+y^2)^1.5,-y/(x^2+y^2)^1.5],x=-1..1,y=-1..1); fieldplot([-x/(x^2+y^2)^1.5,-y/(x^2+y^2)^1.5],x=-1..1,y=-1..1,grid=[8,8]); fieldplot([-x/(x^2+y^2)^1.5,-y/(x^2+y^2)^1.5],x=-1..1,y=-1..1,grid=[7,7]);

>

Download fieldplots_1.mw

Troubling output only maple and or carl can assist...

Asked by: Adam Ledger 360

August 29 2019

0 4

I am trying to use the StringTools package to extract the URLs from the html file exported from Microsoft Edge when i wish to transfer these to another browser, in a text file without all of the nonsense I havent learnt yet.

I just want to trim the file name to set up a Boolean function to check it's update for the day and the output went crazy and decided to spoil my day again

>

(1)

>	$currentdir("G:\\Computer Science\\EDGE\\fav_exports"):$

>	$if is(currentdir() = "G:\\Computer Science\\EDGE\\fav_exports") = true then "Edge favorites usb import html directory is the current file path" end if;$

(2)

>

(3)

>

(4)

>

Error, (in StringTools:-Delete) invalid range

>

(5)

>

Download microsoft_edge_fav_import_fail.mw

Edit: I have gotten closer with the following:

>

(1)

>	$currentdir("G:\\Computer Science\\EDGE\\fav_exports"):$

>	$if is(currentdir() = "G:\\Computer Science\\EDGE\\fav_exports") = true then "Edge favorites usb import html directory is the current file path" end if;$

(2)

>

(3)

>

(4)

>

(5)

>

(6)

>

Error, (in StringTools:-Delete) invalid range

>

(7)

>

Download microsoft_edge_fav_import_fail2.mw

Statistical distributions accept non integer degre...

Asked by: sand15 917

August 29 2019

1 5

Hi,

In statistics a "degree of freedom" is a strictly positive integer.

The three distributions ChiSquare, StudentT and FRatio from package Statistics have degrees of freedom as parameters. Nevertheless they accept any strictly positive real values for them.
(one can verify that their "Conditions" attribute is of the form [0 < n] instead of [n::posint]).

I think this ought to be corrected in future versions

A=B but Maple does not want to simplify arctanh(A...

Asked by: nm 11393

August 29 2019

2 4

A=B but not able to simplify arctanh(A)-arctanh(B) to be zero. Why? Is there a workaround? Using Maple 2019.1

>

restart;

>	A:=((ysqrt(3) + 3)sqrt(3))/(6sqrt(y^2 + 1)); B:=(y + sqrt(3))/(2sqrt(y^2 + 1)); simplify(A-B)

(1/6)*(y*3^(1/2)+3)*3^(1/2)/(y^2+1)^(1/2)

(1/2)*(y+3^(1/2))/(y^2+1)^(1/2)

>	simplify(arctanh(A)-arctanh(B))

arctanh((1/6)*(y*3^(1/2)+3)*3^(1/2)/(y^2+1)^(1/2))-arctanh((1/2)*(y+3^(1/2))/(y^2+1)^(1/2))

>	simplify(arctanh(A)-arctanh(B),trig)

arctanh((1/6)*(y*3^(1/2)+3)*3^(1/2)/(y^2+1)^(1/2))-arctanh((1/2)*(y+3^(1/2))/(y^2+1)^(1/2))

>	simplify(arctanh(A)-arctanh(B)) assuming positive

arctanh((1/6)*(y*3^(1/2)+3)*3^(1/2)/(y^2+1)^(1/2))-arctanh((1/2)*(y+3^(1/2))/(y^2+1)^(1/2))

>	simplify(arctanh(A)-arctanh(B),trig) assuming positive

arctanh((1/6)*(y*3^(1/2)+3)*3^(1/2)/(y^2+1)^(1/2))-arctanh((1/2)*(y+3^(1/2))/(y^2+1)^(1/2))

>	plot(arctanh(A),y=-Pi..Pi)

>	plot(arctanh(B),y=-Pi..Pi)

>

Download will_not_simplify.mw

Compare to Mathematica:

Similar algebraic equations...

Asked by: Muhammad Usman 245

August 28 2019

0 2

Dear Users!
Hope you all are fine with everything. How we can identify the same equations from a number of equations using maple command, like
Eq1:=5.09295817894067*`τu`[1, 1]-30.5577490736439*`τu`[2, 1]+178.253536262923*`τu`[3, 1]-30.5577490736439*`τu`[1, 2]+183.346494441862*`τu`[2, 2]-1069.52121757753*`τu`[3, 2]+178.253536262923*`τu`[1, 3]-1069.52121757753*`τu`[2, 3]+6238.87376920228*`τu`[3, 3];
Eq2:=5.09295817894067*`τu`[1, 1]+10.1859163578814*`τu`[2, 1]+15.2788745368241*`τu`[3, 1]-30.5577490736439*`τu`[1, 2]-61.1154981472883*`τu`[2, 2]-91.6732472209439*`τu`[3, 2]+178.253536262923*`τu`[1, 3]+356.507072525849*`τu`[2, 3]+534.760608788841*`τu`[3, 3]-3/7;
Eq3:=5.09295817894067*`τu`[1, 1]-30.5577490736439*`τu`[2, 1]+178.253536262923*`τu`[3, 1]+10.1859163578814*`τu`[1, 2]-61.1154981472883*`τu`[2, 2]+356.507072525849*`τu`[3, 2]+15.2788745368241*`τu`[1, 3]-91.6732472209439*`τu`[2, 3]+534.760608788841*`τu`[3, 3]-9/7;
Eq4:=5.09295817894067*`τu`[1, 1]+10.1859163578814*`τu`[2, 1]+15.2788745368241*`τu`[3, 1]+10.1859163578814*`τu`[1, 2]+20.3718327157631*`τu`[2, 2]+30.5577490736484*`τu`[3, 2]+15.2788745368241*`τu`[1, 3]+30.5577490736484*`τu`[2, 3]+45.8366236104784*`τu`[3, 3]-12/7;
Eq5:=5.09295817894067*`τu`[1, 1]-30.5577490736439*`τu`[2, 1]+178.253536262923*`τu`[3, 1]+50.9295817894067*`τu`[1, 2]-305.577490736439*`τu`[2, 2]+1782.53536262923*`τu`[3, 2]+504.202859715131*`τu`[1, 3]-3025.21715829077*`τu`[2, 3]+17647.1000900295*`τu`[3, 3]-18/7;
Eq6:=5.09295817894067*`τu`[1, 1]+10.1859163578814*`τu`[2, 1]+15.2788745368241*`τu`[3, 1]+50.9295817894067*`τu`[1, 2]+101.859163578814*`τu`[2, 2]+152.788745368241*`τu`[3, 2]+504.202859715131*`τu`[1, 3]+1008.40571943027*`τu`[2, 3]+1512.60857914560*`τu`[3, 3]-3;
Eq7:=5.09295817894067*`τu`[1, 1]+10.1859163578814*`τu`[2, 1]+15.2788745368241*`τu`[3, 1]-30.5577490736439*`τu`[1, 2]-61.1154981472883*`τu`[2, 2]-91.6732472209439*`τu`[3, 2]+178.253536262923*`τu`[1, 3]+356.507072525849*`τu`[2, 3]+534.760608788841*`τu`[3, 3]-3/7;
Eq8:=5.09295817894067*`τu`[1, 1]+10.1859163578814*`τu`[2, 1]+15.2788745368241*`τu`[3, 1]+10.1859163578814*`τu`[1, 2]+20.3718327157631*`τu`[2, 2]+30.5577490736484*`τu`[3, 2]+15.2788745368241*`τu`[1, 3]+30.5577490736484*`τu`[2, 3]+45.8366236104784*`τu`[3, 3]-12/7;
Eq9:=41.7622570673196*`τu`[3, 1]+41.7622570673196*`τu`[1, 3]+15.2788745368220*`τu`[1, 1]+83.5245141346398*`τu`[2, 3]+30.5577490736443*`τu`[2, 1]+113.063671572516*`τu`[3, 3]+83.5245141346398*`τu`[3, 2]+30.5577490736443*`τu`[1, 2]+61.1154981472892*`τu`[2, 2];
In above equations Eq2 and Eq7; Eq4 and Eq8 are same. If I have set of 100 equation how I can identify similar equations?
@acer @Kitonum @Preben Alsholm

Required; a physics explanation...

Asked by: Earl 985

August 28 2019

2 4

The uploaded worksheet describes a mechanics scenario which I would like to animate.

While I understand the expression for the kinetic energy of the torus, the term containing cos(theta) within the expression for the KE of the pearl baffles me.

From which physics aspect of the scenario does this term derive?

Pearl_in_torus.mw

Why does the tilde operator sometimes fail?...

Asked by: mmcdara 7896

August 28 2019

1 3

Hi,

While trying to convert into integers a sample S drawn from a binomial distribution, I've observed that round~(S) didn't do the job while map(round, S) did it.

First question: why the first syntax and the second one are not equivalent on this case?

I investigated a little bit further by applying round~ on a row vector T of Hfloats (thus T and S are "identical")

Second question: While round~(S) doesn't work but round~(T) does?

>

restart

>	S := Statistics:-Sample(Binomial(10, 0.5), 2); round~(S); # Why round~(S) doesn't return integers map(round, S); # but map(round, S) does? lprint(S)

Vector[row](2, {1 = HFloat(6.), 2 = HFloat(7.)}, datatype = float[8], storage = rectangular, order = Fortran_order, shape = [])

>	# Evaluation of round~(T) on a vector of Hfloats T := Vector[row](2, [HFloat(6.), HFloat(3.)]); lprint(S); round~(T); # round~(T) returns integers,

Vector[row](2, {1 = HFloat(6.), 2 = HFloat(7.)}, datatype = float[8], storage = rectangular, order = Fortran_order, shape = [])

(1)

>

Download Tilde_versus_map.mw

How can i make assumptions for all subscript-varia...

Asked by: Kasp262e 35

August 28 2019

2 9

Hello,

In this simple example in Maple 2019:

k[1] := 16;

solve(k[2]^2 = k[1], {k[2]}, useassumptions) assuming 0 < k;

The result of the solve is

{k[2] = 4}, {k[2] = -4}

which is not what I'm expecting.

I'm expecting

{k[2] = 4}

I'm trying to assume that both the variable named k[1] and the variable named k[2] are greater than 0 by assuming that 0 < k.
My goal is a way to make the same assumption for variables with the same base but different subscripts.
How can I do this?

Thanks in advance.

Combining and converting units...

Asked by: Oliveira 195

August 28 2019

0 5

>

Note: To enter units, I used the unit key (blue) in the Units palette.

When I use the combine and simplify functions to manipulate temperature units, Maple returns a wrong answer, as we can see below;

>

(1)

>

(2)

The quantity 20 Celsius is not converted correctly. However, for other types of dimensions, the combine and simplify functions work correctly.

>

(1804/25)*Units:-Unit(m)

(3)

>

(1804/25)*Units:-Unit(m)

(4)

>

Another strange thing happens with the convert function, with temperature units. When we use the same source unit, the convert function deletes the unit, leaving only the quantity.

>

(5)

I do not understand why this occurs.

>

(6)

I do not understand why this occurs.

Oliveira

Download Matching_units.mw

lprint output (format)...

Asked by: vv 13867

August 28 2019

3 6

If I copy the output of a lprint command e.g.
lprint(<1,2;3,4>);

Matrix(2,2,{(1, 1) = 1, (1, 2) = 2, (2, 1) = 3, (2, 2) = 4},datatype = anything
,storage = rectangular,order = Fortran_order,shape = [])

and paste it in a new execution group, I obtain a "Line print output" instead of a Maple (1D) input,
so it cannot be executed.
(Of course, it's possible to paste in Notepad to remove the format, but it's annoying.)

This happens in Maple 2019, Windows 64, Worksheet mode, 1D input; but not all the time (sometimes it is as it used to be).
Do you see the same behavior?

Statistics fails to reject invalid parameter value...

Asked by: mmcdara 7896

August 27 2019

2 2

Maple doesn't completely check the condition on the number of trials "n" for Binomial and NegativeBinomial distributions (package Statistics).
The attribute "Conditions" explicitely says that n must be a strictly positive integer but no strictly positive real valuereturna an error (ok, it would be stupid to set n to a non integer value !!!).

I think it is a default that ought to be corrected in future releases (this default still exists in Maple 2018)

>

restart

>	kernelopts(version)

(1)

>	with(Statistics):

BINOMIAL DISTRIBUTION

>	X := RandomVariable(Binomial(n, p)): L := [attributes(X)][3]: A := exports(L)

Conditions, ParentName, Parameters, CDF, CharacteristicFunction, Kurtosis, Mean, Median, Mode, MGF, ProbabilityFunction, Skewness, Support, Variance, VariationCoefficient, CDFNumeric, QuantileNumeric, RandomSample, RandomSampleSetup, RandomVariate

(2)

>	L:-Conditions

(3)

>

# Maple should return an error for N is not of type posint
#
# It seems that Sample uses floor(N)

N := 10.49; type(N::posint);
P := 1/2:
X := RandomVariable(Binomial(N, P)):
Mean(X), N*P;
ProbabilityFunction(X, k);
S := Sample(X, 10^6):
Mean(S);

# A non consistent result (only non negative values of k should be accepted)

eval(ProbabilityFunction(X, k), k=evalf(Pi));

piecewise(k < 0, 0, binomial(10.49, k)*(1/2)^k*(1/2)^(10.49-k))

(4)

NEGATIVE BINOMIAL DISTRIBUTION

>	X := RandomVariable(NegativeBinomial(n, p)): L := [attributes(X)][3]: A := exports(L): L:-Conditions

(5)

>	N := 10.49: P := 1/2: X := RandomVariable(NegativeBinomial(N, P)): Mean(X)

Download BinomialLaw.mw

When i type sqrt(25), i get 1.81847767202745*10^(-...

Asked by: gabrielperes46 0

August 27 2019

0 3

Yeah, i have tried evalf[10](sqrt(25)).
How can i get a simple number as answer? I'm loving the software but i just wished i could type in:
int(sin(x), x = 0 .. pi)
and get 2 instead of (2.739493386*10^(-116) + (2.739493386*10^(-116))*I)*pi.
Also, when i type evalf[50](pi), i wish to get all the 50 digits, but i just get \pi :/.
Please help me.

some problems with maple...

Asked by: mehdi jafari 774

August 27 2019

0 6

i have a matrix named S. it has two variables with the names sigma1 and tau. i do some computations with these varibels to obtain a matrix named S_NEW. when i calculate S_NEW with parameters and then i substitute parameter tau with zero i got the answer a zero Matrix. but when i put tau=0 at the initiation of my code, i got another answer. what is the problem?

the second issue is related with the name of parametes in maple. when the varible has the name sigma1 (and tau=0), the matrix S_NEW is a matrix with the only component of (1,1). when i change the parameter name to sigma the matrix S_NEW is a matrix with the only component of (3,3). where is the problem?

>	restart:with(LinearAlgebra):

>

tau:=0;

(1)

>	S:=Matrix(3,[[sigma1,tau,0],[tau,0,0],[0,0,0]]):B1:=Matrix(3):

>	A12,B12:=(Eigenvectors(S)):

>	V12:= Matrix(Normalize~([Column(B12,1..3)],Euclidean)):

>	S_NEW:=simplify(V12^+.S.V12) assuming real ;

Matrix(3, 3, {(1, 1) = sigma1, (1, 2) = 0, (1, 3) = 0, (2, 1) = 0, (2, 2) = 0, (2, 3) = 0, (3, 1) = 0, (3, 2) = 0, (3, 3) = 0})

(2)

>	eval(S_NEW,tau=0)

Matrix(3, 3, {(1, 1) = sigma1, (1, 2) = 0, (1, 3) = 0, (2, 1) = 0, (2, 2) = 0, (2, 3) = 0, (3, 1) = 0, (3, 2) = 0, (3, 3) = 0})

(3)

>

Download problem.mw

Physics package Determinant...

Asked by: Ribeyre 10

August 27 2019

2 4

Hello,

I have installed the Physics Package with:

PackageTools:-Install("5137472255164416", version = 329, overwrite)

I have a question about the calculation of the Tensor determinant:

I use two ways to calculate the determinant of the same matrix:

The first with Physics package and the second with LinearAlgebra Package:

It is easy to calculate analytically the result it is : -1

But Physics Package gives : +1 and LinearAlgebra gives: -1

My question is why I found +1 with Physics Package : What I doing wrong ?.

Please find my source hereafter:

**************************************************

restart

with(Physics)

Setup(coordinates = {X = [t, x, y, z]}, dimension = 4, metric = {(1, 1) = 1, (2, 2) = -1, (3, 3) = -1, (4, 4) = -1}, signature = `+---`, mathematicalnotation = true)

Define(H[mu, nu] = Matrix(4, {(1, 1) = 1+h, (1, 2) = h, (2, 2) = -1+h, (3, 3) = -1, (4, 4) = -1}, shape = symmetric))

H[]

H[determinant]

with(LinearAlgebra)

B := Matrix(4, {(1, 1) = 1+h, (1, 2) = h, (2, 2) = -1+h, (3, 3) = -1, (4, 4) = -1}, shape = symmetric)

Determinant(B)

***************************************

Thanks for your answer,

Sincerely yours

Xavier

why rewriting the ODE changes it classification by...

Asked by: nm 11393

August 27 2019

0 3

This for me seems strange. A first oder ODE of degree one of form A+B*y'=0. Asking Maple for its classification, it gives exact AND rational. After rewriting it in the form y'=f(x,y) , now Maple says it is rational only. It no longer recognize it as exact.

How could this be possible? It is the same ODE, just rewrittng differently. Maple 2019.1 on windows.

>

restart;

>	Typesetting:-Settings(typesetprime=true):

>	ode:=2x/y(x)-y(x)/(x^2+y(x)^2)+(-x^2/y(x)^2+x/(x^2+y(x)^2))diff(y(x),x) = 0; DEtools:-odeadvisor(ode);

2*x/y(x)-y(x)/(x^2+y(x)^2)+(-x^2/y(x)^2+x/(x^2+y(x)^2))*(diff(y(x), x)) = 0

>	dsolve(ode)

>	new_ode:=convert(ode,D); #so I can solve for y' RHS:=solve(new_ode,D(y)(x));

2*x/y(x)-y(x)/(x^2+y(x)^2)+(-x^2/y(x)^2+x/(x^2+y(x)^2))*(D(y))(x) = 0

(2*x^3+2*x*y(x)^2-y(x)^2)*y(x)/(x*(x^3+x*y(x)^2-y(x)^2))

>	new_ode:=diff(y(x),x)=RHS; DEtools:-odeadvisor(new_ode);

diff(y(x), x) = (2*x^3+2*x*y(x)^2-y(x)^2)*y(x)/(x*(x^3+x*y(x)^2-y(x)^2))

>	dsolve(new_ode)

_C1-arctanh((-2/(x^4*(1/y(x)^2+(x-1)/x^3)))^(1/2)*x/((-2*x+2)/(x^3*(1/y(x)^2+(x-1)/x^3))+2)^(1/2))+((-2*x+2)/(x^3*(1/y(x)^2+(x-1)/x^3))+2)^(1/2)/(-2/(x^4*(1/y(x)^2+(x-1)/x^3)))^(1/2) = 0

>

Download why_type_changed.mw

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MaplePrimes Questions

The plots:-fieldplot grid option can give a strang...

Troubling output only maple and or carl can assist...

Statistical distributions accept non integer degre...

A=B but Maple does not want to simplify arctanh(A...

Similar algebraic equations...

Required; a physics explanation...

Why does the tilde operator sometimes fail?...

How can i make assumptions for all subscript-varia...

Combining and converting units...

lprint output (format)...

Statistics fails to reject invalid parameter value...

When i type sqrt(25), i get 1.81847767202745*10^(-...

some problems with maple...

Physics package Determinant...

why rewriting the ODE changes it classification by...

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