9 years, 13 days

## How to construct a Matrix ?...

Maple 2015

Hi,

• 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 ?

## How to deallocate memory ?...

Maple 2016

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 ?

## How to refine the piecewise output of ds...

Maple 2015

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.

## How to print units in a table-structured...

Maple 2015

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

## How to find the dependent variables of a...

Maple

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)}.