I need to create n-order tensor filled with any symbolic variable, for exemple 'x', but "symbol" option works only on vectors and matrix, so i don't know how to do that on n-order array.

X := Vector(3, symbol = x);#------ Work
Matrix(3, 3, symbol = x);#------ Work

Array(1 .. 3, 1 .. 3, 1 .. 3, symbol = x);
Error, argument `symbol = x` is incorrect or out of order

And 2nd problem thet globaly i need to create symmetric n-order tensor with symmitry for any pair of index and with contraction for any couple of indexes equal to zero. As i understend i need to create a big list of equations for every individual pair of index and 2 conditions (contraction and symmitry) and solve it to get a match and combination of independent index and paste values in them?

How do I filter a DataFrame using a value in a string column?
I have a CSV file containing records. Some columns are numbers, others are strings.
The examples in the tutorials are good for filtering on numbers but I can't see how to filter using a string.

ie I have 1300 records with ID, Name, Region, enrolments, ...
enrolments is a number and I can filter on that.
Region is a column of strings. I want to filter on that and work with all records from a specific region.

Thanks,
David Moss

Dear all,

I am looking at the help page for reading json files, but it is too advanced for me to understand...

Can anyone give an easy example where a json file is read into a variable and printing the data structure?

Hugs,
Louise =)

I can draw a triangle using the geomtry package:

point(A, 0, 0), point(B, 2, 1), point(C, 2, 0); triangle(T, [A, B, C])
d := draw(T, axes = none, color = black); t := textplot([[.227, 0.60e-1, typeset(theta)], [1.1, 0, typeset(k__2)]])
display(t,d)

The result is as below.

I would like to place the label k2 below the line but negative numbers do not work. I would like to put a label k1 to the right of
the opposite side but there is no room,  and finally I would like to put sqrt(k1^2+k2^2) above the hypotenuse slanted to be
parallel with the hypotenuse if possible.

Bug_in_integrate.mw

M_Iwaniuk

of a (concrete/general) triangle, making use of Maple tools in an efficient way?  Mathematica applies the barycentric coordinates and the Dirichlet distribution to this end. More generally, how to efficiently choose a random point in a given bounded region?

Hello all,

I have a hash structure with arrays in a YAML file that I would like to read in Maple.

Does there exist a module, so I can read it?

When generating the list of all the permutations of  [$1..10]  we get an error:

combinat[permute]([$ 1 .. 10]);

    Error, (in combinat:-permute) Maple was unable to allocate enough memory to complete this computation. Please see ?alloc

But if the same problem to solve using a simple custom procedure, there is no any problems:

restart;

Permute := proc (L::list)

local n;

n := nops(L);

if nops(L) = 1 then return [L[1 .. 1]] else

[seq(seq([op(p[1 .. k-1]), L[1], p[k .. n-1][]], k = 1 .. n), p = Permute(L[2 .. n]))] end if;

end proc:

L := CodeTools[Usage](Permute([$ 1 .. 10])):

nops(L);

Hi 

My teacher (im studing Technology Management and Marine engineering) only allow that we use maple if we display the results between calculations. Is that posible:

a := 4;

b := 5;

Instead of :

a+b=9

I want it displayed as:

a+b= 4+5= 9;

or just

4+5 = 9; where a and b are Automatically replaced with the respective values, when i run the !!! button

A lot of my calculations are done by defining the variables in the top. 

Any ideas??

Thanks in advance.

Best regards  Carsten Moller

Is there currently any way to perform Feynman integration after applying the Feynman rules for various electrodynamics processes? 

Can maple 2016 do renormalization of integrals? If we cannot currently do any of these, when will this features be available? Thank You very much.

Maple 2016.1a now available, fixes issues reported here http://www.mapleprimes.com/questions/211561-Why-Does-Maple-20161-Improperly-Treat-X2

Thank you Maplesoft for your quick response to this issue.

hi,

i'm trying to figure out where i did a mistake by coding reducedEchelonForm.

with(LinearAlgebra):
reduced:=proc(M)
 local l:=1, m:=RowDimension(M),n:=ColumnDimension(M),i,j; # l current column
 for i from 1 to m do # going trough every row item
  if n<l then # ColumnDimension need to be bigger than current column
   return M;
  end if;
 j:=i; # given current row item
 while M[j,l]=0 do # search for first rom item unequal zero
  j:=j+1;
  if m<j then # end of row
   j=i;
   l=l+1;
   if n<l then # end of rows and columns -> finish
    return M;
  end if;
 end if;
end do;
M:= perm(m,n,j,i).M; #permute row j and i
if not(M[i,l]=0) then # multiply row i with M[i,l])^(-1)
 M:= multiplikation(m,n,i,(M[i,l])^(-1)).M;
end if;
for j from 1 to m do # subtract every row j with row i for M[j,l]-times
 if not(j=i) then
  M:= addition(m,n,j,i,-M[j,l]).M;
 end if;
end do;
l:=l+1; # increase l by 1, next iteration i increase either
end do;
end proc:

Hint: perm(...),multiplikation(...) and addition(...) are the elementary matrices. They are working.

Now i got an error by running it: 

L:=Matrix(2,3,[1,2,3,4,5,6]);
reduced(L);
Error, (in reduced) invalid left hand side in assignment

Can someone explain me these error? And maybe a hint what i need to fix in my code?

Greets felix

Hello

I have a subscripts error, or it seems to be an error.

As you can see on the picture, then I have defined the varible I__K, but when I need it again I get another result or It seems to be another result that looks like this I[K]. I use the esc buttom to recall the varible.

Are there anybody that has a solution to this? I have been looking at other treads, but there seems not to be a solution that works or maybe I'm looking the wrong places.

Regards

Heide

Hello everyone!

I am wondering why the Tabulate command does not work with Explore. E.g.:

Explore(`DocumentTools:-Tabulate`([plot(sin(a*x)), plot(cos(x-a))]), parameters = [[a = 0 .. 10, controller = slider]])

I know that I can display an array of plots with the display(Array([....])) which works fine with explore but Tabulate is another good way to display multiple plots and it gives better control over individual plots properties (e.g. setting different size to different plots). Is this a bug or Tabulate is just not meant to work in that context?  

When experimenting with Maple 2016.1, I found several issues. One I have seen on MaplePrimes before (regarding "Error, incorrect syntax in parse: `;` unexpected (near 4th character of parsed string)" when evaluating an integral, for example, or trying to plot something), but another I have not seen - it may be related to the previous issue. Below is a document that contains some of the various errors I found. What is going on? It evaluates certain things correctly, but, in the integral, it treats "x^2" like a whole new variable (the integral of x^2 with respect to x from 0 to 2 it says is 2x^2, not 8/3). The same thing results in trying to plot x^2 (not shown), giving the same error if I were to say something like "plot(t,x=0..2)" - it cannot determine the plotting variable.
 

Download bad_maple.mw 

Any ideas? Are the two things (the Error, incorrect syntax in parse: `;` unexpected (near 4th character of parsed string) message and the bad integral value) related?