sand15

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These are questions asked by sand15

Hi,

Could you please help me in solving this problem ?

  • N is the number of row, about 10^4 in real applications
  • P is the number of columns (about 5)
  • A and B are two NxP matrices
  • C is the Nx(2P) matrix defined by
    • its 2*k-1 th column is the k th column of A
    • its 2*k th column is the k th column of B


What is the fastest and less memory consumming way to construct this matrix C ?

Thanks in advance

 

 

Hi,

As a notional example those instructions generate 21 variables and around 4 Giga Bytes of data (bottom right of the Maple window ; roughly the same value read from the windows manager)

with(Statistics):
for n from 1 to 10 do
   X__||n := RandomVariable(Uniform(0,1)):
   S__||n := Sample(X__||n, 10^8)
end do:

I want to clean some part of the  memory ; for instance all the S__||n.
The following doesn't work

KeepVars := { seq(X__||n, n=1..10)}:
unassign({anames(user)} minus KeepVars ) ;
gc();


Is there a way to deallocate the memory occupied by some of my user variables ?
 

Hi there,

The command

           dsolve(MyOde, numeric, range=MyRange, method=rosenbrock, output=piecewise)

returns a list of solution pieces which is not sufficiently dense according to how I intend to use it.


Is there a possibility to impose the "number of pieces" or the positions of the "breaks" in this command ?

Thanks in advance for any suggestion.

 

Hi everybody,

 

I want to plot many curves in the form of a table.

For instance, let    p := plot(x, x=0..1, labels=[x*Unit('m'), y*Unit('m')]):

The command   plots:-display(p)  returns a plot  with labels x [[m]] and y [[m]], just as expected.

But the commands (remember I have several plots)
                             plots:-display(<p>);                              # and the generalization plots:-display(<p | p>)
                             DocumentTools:-Tabulate([p]);           # and the generalizationDocumentTools:-Tabulate([p,p])
both provide labels  x Units:-Unit('m') and  y Units:-Unit('m')

Is there a way to fix this and obtain plots withe the expected labels ?

Thank to all of you for yout help

Hi everybody,

I have differential equation of the form eq := diff(x(t), t) = x(t) + 1  and I want to find the name of the dependent variable (more generally this issue concerns a differential system in N dependent variables).

How should I use “indets” in order to obtain {t, x(t)} ?

(indets(eq, name) returns {t}, while indets(eq, function) returns {t, x(t), d/dt x(t)}.

Thanks in advance

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