## building a matrix from a bivariable function...

 (1)

 (2)

 (3)

 (4)

im trying to build a matrix starting from a function, so i can later use this matrix to get a more simple function using linearfit from the statistics package, like a kind of regression.

i want to get a matrix starting from h__1(T1,T__1s) so it has to be a 3 columns matrix (T__1,T__1s,h__1). so as you can see, i have got the functions h__1 and h__2, but i need to evaluate it at differents values for T__1 and T__1s and building a kind of value-table in matrix form.

for h__1, T__1 must be higher than T__1s, or you could get imaginary values, don't know if that important for building the matrix.

thank you very much for your help.

## Best way to fill a matrix using a math function an...

Bear with me, while I've used Maple V, I've never done any actual programming in Maple as I've almost entirely used Matlab.  Right now I've got an issue with trying to fill a square matrix using a sinc function [(sin(Pi*x)/(Pi*x)].  Here's my procedure:

Note that the arguments for sin and for the denominator are written as they are so as to define the domain of  the sinc function as [-m/2,m/2] along a row and [-n/2,n/2] along a column of the matrix I want to fill and so that I the arguments can have decimal values.  Also note the conditional statements there because when the sine argument and the denominator yields Pi*0, the function equals 1 despite the zero in the denominator.

So I'm unsure how to fill a matrix of some size m x n using the procedure (or a function if that makes the programming easier).  Here's how I would write the code for Matlab:

Z=zeros(2001,2001);
X=(-5:.005:5)';
Y=(-5:.005:5)';

count1=1;

for j=-5:.005:5
count2=1;
for k=-5:.005:5
Z(count1,count2)=sinc(k)^2*sinc(j)^2;
count2=count2+1;
end
count1=count1+1;
end

Given my meager experience writing Maple code, I'm a bit flumoxed.

Thanks, and don't feel like you have to be gentle. No one ever accused me of writing elegant code.

Thanks

## Numerical Solutions to Matrix/Lattice Based Proble...

Hi, so I have few problems here. I need to;

Create a MxN Matrix/Lattice, where N and M can be any positive integer, that contains a random selection of -1/1s at each entry.

Need to sum every entry, then multiply by -1 to find “H”.

Need to multiply each neighbour to find its bond energy, so if it’s the same you get 1 else -1, but only its direct neighbours once, so if it was a 2x2 matrix there would be only 4 values and then sum them.

I don’t seem to be able to set up the code so that it does it for any size matrix, as I only know how to write it out basic for a 2x2. Also, not so important, but I wanted to know if could create a loop that would find every iteration of possible setups i.e. for a 2x1 you can have 1.1, -1.1, 1.-1, -1.-1. And then give the solutions outlined earlier for each of the the possibilities [There being 2MxN ]

## how do I create a 15 x 15 matrix in maple?...

Am a post graduate student. am using maple as soft ware.. How can I create a 15 x 15 matrix in maple?

## Wronskian for any list of functions...

hi i have this code that doesnt work and I cant find the problem. I cant make the matrix include more than 2 rows. i want this to give me the whole nxn matrix, and then the solution to the wronskian.

can you pls help?:) thanks!

with*linalg;
funcs := [x, 3*x, x^2, 5*x];
n := nops(funcs);
print*n;
printlevel := n;
count := 1;
listM[count] := funcs;
for i from 2 to n do listN := diff(funcs, `\$`(x, i-1));
count := count+1;
listM[count] := listN end do;
M := convert(listM, matrix);
det(M)

## matrix equations...

Hello guys, i have some matrix equations.

A^(T)*X+X*A+Q = 0 , where A,Q - matrixs, X - unknown matrix, i need to solve this.

i tried to solve this from http://www.mapleprimes.com/questions/200940-How-To-Solve-Matrix-Equation-Problem-In-Maple#answer203570 methods, but not successfully.

How can to solve this problem?

multMatrix.mw

thx.

## Why is Determinant often incorrect for matrices wi...

When I use the Determinant function on a matrix with (single variable) polynomial entries with real coefficients I often get an incorrect answer. I know the answers are incorrect because they have a higher degree or a lower lowest degree than is possible given the matrix elements.

However, when I replace the coefficients in the polynomials with rational numbers or I put in the option method=minor, I get the correct answer.

The problem seems to be roundoff error. However, the important error is not simply small changes in the resulting polynomial. The important error is the presence of entirely incorrect powers of the variable and not with very small coefficients.

How does this happen and why does the help page for Determinant( ) not warn of this behavior? In particuiar, why does the help page not say that using Gaussian elimination (i.e., the default) will often give incorrect answers in such cases, but using method=minor will work? Is this behavior known? I cannot find any reference to it on the internet.

## Why wouldn't subs work?...

Hello people in maple primes

I have a question, which is about the matrix shown in http://www.mapleprimes.com/questions/217852-HOW-I-Convert-Root-Of-In-To-Another-Common-Form

Why can't C below be shown with beta?

A := Matrix(3, 3, [[-a, a, 0], [0, 0, -sqrt(l*b*c*(j+k))/(j+k)], [2*j*sqrt(l*b*c*(j+k))/((j+k)*l), 2*k*sqrt(l*b*c*(j+k))/((j+k)*l), -c]]);
B:=subs(l*b*c*(j+k)=alpha,A);
C:=subs(j*alpha^(1/2) = beta,B);
e:=subs(alpha^(1/2) = gamma,B);

Best wishes.

taro

## how to creat a matrix from a many array...

Dear Pros, I'm a biginer so I have a question about my program.

I have a lot of arrays which are result from 2 while loop. Now, I want creat a matrix from them but i can't. So, could you help me to do it.

For detail:

V[1]:=[ 1 2 3]

V[2]:=[2 3 4]

V[3]:=[3 4 5]

V[4]:=[2 6 7]

V[5]:=[7 8 9]

...

V[n]

with type of V[i] is a array.

I searched and found a solution by manual to create a matrix as follow:

V_matrix:=<V[1],V[2],V[3]>

but in this case i can't but manual with n=100

Thank a lots.

## Solving a matrix with LinearSolve ...

I have tried to solve a matrix with the function "LinearSolve" as seen in the picture, but instead of solving it just gives me back the operation i wrote (3). My which is to solve an equation system a quick as possible - have a templet fill in the matrix and press enter. I thought this "LinearSolve" function was the easiest way of doing. I know that I can right click and choose the function, but I want it as a command.

Any solutions on how to use the "LinearSolve" command to solve an equation system?

## how to use Riemann matrix to output Riemann surfac...

how to use Riemann matrix to output Riemann surface?

and plot this surface?

with(algcurves):
f:=y^3+2*x^7-x^3*y;
pm:=periodmatrix(f,x,y);
evalf(pm, 5);
rm:=evalf(periodmatrix(f,x,y,Riemann),10);
M := rm;
A := proc (x, y) options operator, arrow; RiemannTheta([x, y], M, [], 0.1e-1, output = list)[2] end proc;
plot3d(Re(A(x+I*y, 0)), x = 0 .. 1, y = 0 .. 4, grid = [40, 40]);

is this graph Riemann Surface?

if so, how to convert A into polynomials?

## Workbook issues...

Dear Maple users

I have done some experiments with the new Workbook feature in Maple 2016. It is a very welcome addition, indeed. Earlier I have created Maple files in which data from an external Excel file was imported and being used for certain calculations. In order to make recalculations work properly, one need to let the Excel file follow the Maple file. That's where a Workbook come in handy! I tried placing those two files in a Workbook. It didn't work completely as advertised, I think. I moved the Workbook to another location on the harddrive to make sure it wouldn't interfere with the original files outside the Workbook. Then I recalculated the Maple document inside the Workbook. The good thing: The data from the Excel file was still present. The bad thing: If I changed some data in the Excel file inside the Workbook, it didn't register in the Maple file when updating it!

Maybe I should explain that I did import data from the Excel file into Maple via the menu: Tools > Assistants > Import Data... The data was retrieved as a matrix within the Maple file and assigned to a variable and used for plots ...

Why doesn't the above procedure work properly? I hope one don't need to use the Workbook URI to reference files within the workbook. It is not that userfriendly!

Regards,

Erik

## How do I save a matrix in an intermediate step of ...

I am working on an iterative code where I need to save a matrix in an intermediate step. My code is long and it uses a separate data file. So, I am trying to state my problem taking a simple example.

At first, I define a column matrix A0. Using A0, I do some calculations and test some conditions.
In the next step, I want  to do similar calculations and test some conditions but this time by changing the first element of A0. For the purpose of later use, I need to save the matrix A0 in its original form. I am trying to use the following method but both A0 and A1 (modified A0) turn out to be same.

> restart;
> n := 3;
> A0 := Matrix(n, 1, 1);
> #Do some calculation with A0
> A1 := A0;
> A1[1, 1] := A1[1, 1]+.1*A1[1, 1];
> A1;
> print(A0, A1);

This might be because I set A1:=A0 in the third line. But how do I save A0 in its original form?

## problem with solve...

i want to solve a system , A.b+B.X=0 , which A is 5*5 known matrix, B is 5*2 known matrix , and b is 5*1 and X is 2*1 unknown arbitary matrices ! i want to have solution for b and X . whatever they can be ! just equation to be solved !

 > restart:
 > A:=Matrix(5,[[-0.9800,0,0,-0.0160,0],[1.0000,0,0,0,0],[-2.1900,-9.7800,-0.0280,0.0740,0],[77.3600,-0.7700,-0.2200,-0.6700,0],[0,-79.9700,-0.0300,0.9900,0]]);
 (1)
 > B:=Matrix((5,2),[[-2.44,0.58],[0,0],[0.18,19.62],[-6.48,0],[0,0]]);
 (2)
 > b:=Matrix((5,1),[y[1],y[2],y[3],y[4],y[5]]);
 (3)
 > X:=Matrix((2,1),[[x[1]],[x[2]]])
 (4)
 > M:=A.b+B.X
 (5)
 > eval(M,y[1]=0)
 (6)
 >
 >