## I need some information about `if`...

Hi, I can't find any information what does FI mean, for example: f := proc(x) if x>0 then x else -x fi; end proc: f(-3); or: if iseuler(G) then continue else RETURN (print ("The graph does not have an Euler circuit")) fi; I'm tired of googling already, Maple Help doesn't have any information about fi, what might it be? perhaps some closing declaration instead of 'end if'? I would be grateful for any comments, thanks in advance, Sven

## polynomial from list of coefficients...

is there any way of creating a polynomial in maple from a list of coefficients (i could write my own function, but this is annoying, no?). specifically i would want an inverse to the PolynomialTools:-CoefficientList function, f([1, 2, 3]) would yield me 1 + 2*x + 3*x^2. i cant understand the apparent lack of such an elementary function, i must be missing someting? thanks

## Two plotting queries...

Hiya,

I have two questions...
Firstly when plotting a graph in Maple using plots[display]({A1,A2,A3}), is there anyway to switch the horizontal and vertical axes such that f(z) is on the horizontal axis and z along the vertical?

Secondly, I'm trying to plot a sum at various times t,

c(z,t)
:= Sum(A[n]*Phi[n](z)*exp(-lambda[n]*t), n = 1 .. 10)

## Fitting Imported data to a Gaussian distribution...

I several peaks from emission spectra which I am trying to fit wit a Gaussian distribution.

y = y_0 + A*exp[-{(x-x_0)/(width)}^2

The problem I am running into is I am getting fits which are wrong.  Maple returns:

fit_658 := 1.+1.*exp(.50000000000000*(z-1.)^2)

-7e05+2.7e06*exp(((z-656.1)/9)^2)

Also, I am interested in finding the deviation in the parameters which are found.

## Refactoring Maple code

by: Maple

John Fredsted posted some interesting code dealing with permutations, and I suggested a small improvement.  Here, I want to continue the story of that improvement.  First, let us focus one particular line of code:

```  posMaps,negMaps := seq(map((perm::list) ->
(x::list) -> [seq(op(perm[i],x),i=1..nops(perm))]
,perms),perms in [posPerms,negPerms]);```

which uses a lexically scoped procedure to perform the permutations. The first thing to notice is that `op(perm[i],x)` is really equivalent to `x[perm[i]]`. Now that we have that perky `op` gone, we see that the resulting code expression will return unevaluated if `x` is unknown, unlike `op` which throws an error message (correctly so!). So now instead of using scoping, we can let Maple actually evaluate the inner `perm[i]` calls, and use `unapply` to recover a routine. Putting that together gives us my suggestion:

```posMaps,negMaps := seq(map((perm::list) -> unapply([seq(x[perm[i]],i=1..nops(perm))],x),perms),
perms in [posPerms,negPerms]);```

## Symbolic Vector Manipulation...

I would like to do something like a derivative with respect to a vector or really anything involving a vector (not of a known length or known values) going in and a vector coming out:

diff( Transpose(x) * A * x, x)

Is this possible?

It's just that it is very different if you do x*(x+1) if x is a vector or if x is a scalar.  Does this make sense?

Any tips would be great!

Thanks,

Dave

## A random boolean that has a chance = p of being tr...

Hello,

I have another question. I would like to construct a code, demonstrating the loss of information when sending codewords.  Usually, one assumes that each entry of the codeword has a chance equal to p  (like p=0.17) of being incorrectly sent.  How can I have such a random element in my code?

Thank you,

fredbel6

## Fonts in plots...

I have a 2D and a 3D plot which are close together and I would like them to have a similar look. However, when I set the caption with:

caption=["whatever text I want here", font=[HELVETICA,BOLD,12]]

I get what appears to be different fonts on the two plots.

Any suggestions as to whether I am doing something wrong please?

(And does Maple not allow me to use any font I want?)

Many thanks

Karina

## Trying To Install A User Defined Package...

I downloaded John Fredsted's Gravitation code from the Maple application center, and now I'm trying to get it to be a package.

However, I'm having trouble doing this.

Can anyone help me get to the point where I can access this application as any other manufacturer produced package using the with command ?

v/r,

## easy way to do it?...

Hey

I was discusing Maple and Matlab with one of my friend.

He said that in Matlab he can do

a:=1:12

b:=sin(a)

plot(a,b)

that's easy in matlab to do so

i use

> ptlist:=NULL:
> for n to 12 do
> ptlist:=ptlist,[n,sin(n)]:
> od:
> plot([ptlist]);

do to so

is there any easy way to do that in maple?

like creat a sequence from 1 to 12? ( besides seq(n,n=1..12))

thanks

## how will maple response to non-unique solutions??...

dsolve( {diff(x(t),t)=sqrt(x(t)), x(0)=0}, x(t));

use the theorem to test the ODE ,the solutions are unique

however maple gives me a unique solution?

## include text...

Hello, I would like to create paragraphs and titles shown in black, inserted in my maple worksheet ( I use maple 10), should I change the standard mode?

## Fitting cylinder to data...

I was hoping to fit a cylinder to some data points in 3d space and find the equation of the long axis of the cylinder.

Sample data (actual data much larger matrix):

## Problem with integration when computing power seri...

Hello
I have a problem with Maple. I would like to compute following sum using differentiation:

an:=x^(4*n-3)/(4*n-3)

This power series is convergent for x in (-1,1).

Sum(an,n=1..infinity);

diff(%,x);

s1:=value(%);

pf:=convert(s1,parfrac);

Now when integrating:

subs(x=t,pf);

int(%,t);

the result is: 1/2*arctan(t)-1/4*ln(t-1)+1/4*ln(t+1) .

The problem is that ln(t-1) is not defined for t in (-1,1). This is caused by integration of the equation:

-1/4/(t-1)

which is

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