## cobwebbing...

How do I build a cobweb plot of a recursion equation in Maple?

## how can we interchange indices and entries of a ta...

for example,if we have a table T=table([aa=2, bb=3 cc=4, dd=5]),how can we get another table(2=aa,3=bb,4=cc,5=dd) ?

another question:
if we have table([aa=3,bb=5,cc=1,dd=3]),how can we output indices according to entries' ascending order?

thank you

## forecasting economy using maple...

i would like to know any of you guys have any ideas on forecasting economy. basically using different equations and its command in Maple?

## converting complex numbers...

Is there a way to convert a complex expression into the form a + ib (splitting it into its Re and Im parts) , even if the expression that you want to convert is in terms of a variable?

ie, I have something like f(r) and I want to put it in the form a(r) + i b(r)

## How do I Work with units such us kN (kilo Newtons)...

How do I set maple to work with this units kN (kilo newtons), MN (mega Newtons 1MN= 10^6 N)??'  I'm Just starting with maple. Thanks for your help!

## how to determine temp. distribution in maple...

Hi All,

Would anybody be able to explain to me how to find the steady state temperature distribution in maple using the finite difference method?

Any help wouild be greatly appreciated.

Cheers

Joel

## Converting from Maple to Matlab...

Hi

I am getting the following error in Matlab for an equation that I converted from Maple using the Matlab() command.

"Subscript indices must either be real positive integers or logicals."

Maple does show this warning before giving the Matlab code.

"Warning, the function names {alphaD} are not recognized in the target language"

The equation is the derivative of a function with more than one variable.

Thanks

## undoing one form of symbolic root

by: Maple

In this previous post, an example is shown that demonstrates the potential problems that can arise following symbolic conversions such as from sqrt(x^2)  to x^(1/2).

Here x is an unknown symbol. The difficulties include the fact that, while `sqrt` can be smart about simplifying numeric values (eg. integers, rationals) the `^` operator has no such opportunity. Once the conversion from `sqrt`...

## Fit a Curve to Data...

Hi,

I have some data (points of results -> a list of x - data and a list of corresponding y - data) and I would like to fit a curve to this data.  curves does not fit very well to the data points.

Can anybody give me a method to fit a curve to the data?

Tanks!

The data are:

## Computing the cumulative bivariate normal distribu...

by: Maple

This provides a Maple solution to compute the bivariate normal distribution by recursions for numerical inputs. It works even for extreme cases and handles situations, where usual integration with Maple has serious problems (even after reducing to dimension 1), it seems to be reliable and fast and works in 'arbitrary' precision.

To use it call N2_as_sum(1.0, 2.0, 0.8,  200) to compute the BVN for x = 1.0, y = 2.0 and correlation rho = 0.8 with at most 200 recursion steps (it will stop earlier, if no more improvements can be seen).

## The single argument Complex constructor

by: Maple

The calling sequence in ?complex states only the two argument form 'Complex(x, y)', but later in the section "Description", in a bit confusing way, two rules for the single argument form are stated:

## Thomas Calculus 5.6.15 exercise gets "hypergeom"...

I get "hypergeom" with Thomas Calculus exercise 5.6.15 for some unknown reason. the other exercises don't get this. See it at:

http://i36.tinypic.com/258lzqx.jpg

how can i get rid of the "hypergeom" in the answer ?

## How do I "clear" an array?

by: Maple

I need to do the following. Suppose I have an array, c[ ]. I need to be able to specialize the elements of this array, and then later "clear" the elements, making them indeterminates again. I attempted to do this by creating a temporary holding array

i:='i': for i from 1 to 5 do d[i]:=c[i] end do;
i:='i': for i from 1 to 5 do c[i]:=i end do;
i:='i': for i from 1 to 5 do c[i]:=d[i] end do;

I expected and want the output to be

c[0] c[1] c[2] c[3] c[4] c[5] 1 2 3 4 5 c[0] c[1] c[2] c[3] c[4] c[5]

## Incorrect result of is with abs and infinity...

Hello!

I have just found this incorrect behaviour of is  (Maple 12):

restart;

## Another strange behavior for numeric solution of O...

Hi all,

```> deq := diff(x(t), t) = 3*x(t)/t+(9/2)*t-13;

d         3 x(t)   9
deq := --- x(t) = ------ + - t - 13
dt          t      2
> ci := x(3) = 6;

ci := x(3) = 6
> p := dsolve({ci, deq}, x(t), numeric);

p := proc(x_rkf45)  ...  end;
> plots[odeplot](p, view = [-1 .. 4, -10 .. 10]);

```

```> p(0);

[                                     -8]
[t = 0., x(t) = 8.65023735199754930 10  ]```

but if I do:

```> q := dsolve({ci, deq}, x(t), type = numeric, method = taylorseries);

q := proc(x_taylorseries)  ...  end;
> plots[odeplot](q, view = [-1 .. 4, -10 .. 10]);

> q(0);

[t = 0., x(t) = 0.]
> solex := rhs(dsolve({ci, deq}, x(t)));

9  2   13      3
solex := - - t  + -- t + t
2      2

```

But in cases where I don't know the answer, which should I trust?  here is another one

```> deq := diff(x(t), t) = 1-t-x(t)/t;

d                 x(t)
deq := --- x(t) = 1 - t - ----
dt                 t
> ci := x(1) = 0;

ci := x(1) = 0
> q := dsolve({ci, deq}, x(t), numeric);

q := proc(x_rkf45)  ...  end;
> q(0);

[t = 0., x(t) = 1.73003351210698475]
> plots[odeplot](q);

> solex := rhs(dsolve({ci, deq}, x(t)));

1  2   1      1
solex := - - t  + - t - ---
3      2     6 t
> plot(solex, t = -1 .. 1, -100 .. 100);

and for the finish

> r := dsolve({ci, deq}, x(t), numeric, method = taylorseries);

r := proc(x_taylorseries)  ...  end;
> plots[odeplot](r);
%;
Warning, could not obtain numerical solution at all points, plot may be incomplete

```
```> r(0);
```
```Error, (in r) cannot continue integration past t=0.585794295977905e-4, step size dropped below minimum

```
` `

Thanks in advance for any help

Mario

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