Hello MaplePrimes users

How do I find expressions of an integer as a sum of four squares in Maple?

Hi everyone,

Please, I really need your expertise advice(s) on what i am not doing right in the code attached below. I was actually writing the code on Multi-step DTM, but, instead of continuing from the last point, it starting all over again. Please, your expertise will save a soul here. Regard

Thanks

MsDTM3.mw

Hi, 

I need to plot some correlation matrices C1, C2, ... and I use matrixplot for this.
I would like to use the same absolute scale (-1..+1) for all of them.
For instance is I decide to uses colorscheme=["blue", "white", "red"] I would like blue to correspond to value -1, white to value 0 and red to value 1.
Unfortunately colorscheme set to blue the cell with the mininum value (not necessarily -1) and to red the maximum one (not necessarily +1).
Here is an example

restart:
with(plots):
with(Statistics):
randomize():
N := 10:
P := 3:
A := Sample(Uniform(0, 1), [N, P]):
C := CorrelationMatrix(A):
matrixplot(
  C,
 heights=histogram,
 axes=frame,
​​​​​​​  gap=0.25,
​​​​​​​  color=((x,y)->(C[x,y]+1)/2),
​​​​​​​  orientation=[0, 0, 0],
​​​​​​​  lightmodel=none,
​​​​​​​  tickmarks=[[seq(i+1/2=A||i, i=1..P)], [seq(i+1/2=A||i, i=1..P)], default],
​​​​​​​  labels=[("")$3]​​​​​​​
​​​​​​​  );

​​​​​​​I also tried to use color=((x,y) -> (C[x, y]+1)/2) instead of colorscheme but here again matrixplot uses a local scale defined by the reange of the correlation matrix to plot.

I fixed this by using something like seq(seq(PLOT(POLYGONS(...), i=1..P), j=1..P) instead of matrixplot, but I think it is a shame to do so.

So my question: is it possible to force matrixplot not to use a scale defined by the matrix to plot, but a "user" scale?

PS: I'm using Maple 2015 

Thanks in advance

I have some trouble solving the pde of:
ut + u^2*ux = u, u(x,0) = x, with x::real and t>0.

I think that I have 2 problems.

1.
The first part of the code I define u(x,t) with both the variable rp.
Then I define the variable q copying the definition of u(x,t).
When I try to insert q and u(x,t) in the initial equation - one is able to be reduced to one term while the other isn't.
So I'm not really sure what is happening here.

2.
When I use Maple's pdsolve() I get a result, but when I insert the answer in the initial equation - then it isn't correct.
I tried to show this in the last part of the code.

Download asol1-1.mw

I just  found what seems to be a serious problem and I am not able to figure if it is related to my own installation or not.

After I installed Physics 426 (Published on Sept 17, 2019) using the Maple GUI install button (which now works for my PC), I found I am not able to integrate basic things.

It seems to affect int when using some build in function with definite integration, but it could be others also. I need to test more. 

Could someone see if they get same problem as well?  

Could also someone please remind me of the library  commands to issue in order to remove current Physics version 426 and install earlier Physics version package, say 425, or any other version, so that  to see if this is related to version of a physics package or not?

Download int_not_working.mw

@Torre 

with(DifferentialGeometry);
with(Tensor);
with(LieAlgebras);
DGsetup([x, y], M);
g1 := evalDG(dx &t dx);
Christoffel(g1);
Error, (in DifferentialGeometry:-Tensor:-Christoffel) expected 1st argument to be a metric tensor. Received: _DG([["tensor", M, [["cov_bas", "cov_bas"], []]], [`...`]])

I still get an error.  I was able to succeed in another example (when I copied the whole maple example.

Somehow, I cannot get the correct syntax.

Any help would be welcome.  The only explanation is that somehow the definition of the neutral tensor operator is missing.

Why Maple 2019.1 gives an error when no initial conditions are given for the following heat PDE with periodic BC?

I am using Physics 426 (current version). On windows 10.

When adding ic as some arbitrary function f(x), then the error goes away. But no ic needs to be given to solve this PDE. The answer can be left using arbitrary constants in this case.

I also found that this seems to happen when the BC are periodic. When using the normal Dirichlet B.C. and omitting the initial conditions, the error went away.

Am I doing something wrong or is this a bug?

Download problem_09_20_2019.mw

I'm pretty annoyed with maple because when I try to create proc's it dooes not use tabbing or smart tabbing. This makes writing readable code a chore. Basically it's always screwing up alignment. (it wants to left justify things a lot)...

What's worse is that using the tab key takes one outside the proc rather than adding a tab, making one having to use spaces.

Any way to fix this?

I have an equation to solve 

where  is scalar,  is vector,  is vector,  is a matrix. I need to solve this equation for  but S1 is matrix sow can I tell Maple that S1 is matrix? If we solve the equation with matrix we need to use matrices inverse. If we have to divide by matrix we use the product of the inverse of this matrix.

For example, if I have a function

f:=x->x^3-2x

I want to created csv file containing coordinates of points of the function

(1,...), (1.1,...),...

How to do it?

I want to convert the coordinates to csv file and use this file in originpro to plot a graph that is more beautiful than that of Maple.

Hi,

I have this code to calculate taylor method but I do not know how to write the part about derivative of a function f  inside the loop for ??

restart;
f:=(t,y)->y-t^2+1:
eqn:=diff(y(t),t)=y(t)-t^2+1:
ex:=dsolve({eqn,y(0)=0.5},y(t)):
t[0]:=0:w[0]:=0.5:h:=0.2:ex[0]:=0.5:e[0]:=0:
for n from 1 to 10 do
t[n]:=n*h;ex[n]:=t[n]^2 + 2*t[n] + 1 - exp(t[n])/2;
w[n]:=w[n-1]+h*f(t[n-1],w[n-1])+((h^2/factorial(2))*(f(t[n-1],w[n-1])-2*t[n-1]));
e[n]:=abs(ex[n]-w[n]);
od:

printf(" i | t[i] |(Taylor)w[i] |(exact)y[i] |Error | \n ");for i from 0 to n-1 do
printf("%2.2f| %5.2f  | %5.6f| %5.6f  |  %5.6f | \n", i, t[i], w[i] ,ex[i],e[i]) ;
od;

Download error.mw
 

Download error.mw

Hi i was trying to numerically integrate my freinds model with dsolve, and i am sure that I have put all the right components in the command as described in the help page, but it doesn't work. (Here is a worksheet with the model Lindas_signal_transduction_model.mw )

What is the problem with the way I have called the function?
Does anyone have a mental checklist that they use for dsolve commands? because I often struggle with making them work.

Can you help me

myproc := proc () local img1, img2, img3;

with(DocumentTools); with(DocumentTools:-Layout);

img1 := "c:\\1.jpg"; img2 := "c:\\2.jpg"; img3 := "c:\\3.jpg";

print("Title 1 row 1, picture 1"); print(img1); print("Title 2 row 2, picture 2");

print(img2); print("Title 3 row 3, picture 3"); print(img3);

print("The End");

end proc

Download insert_picture.mw

print monitor

The problem is that this function only works for integer exponents

Is there another way to overcome this

Download question_for_rif