Hi, I am very new to Maple and i was using Maple with a code that was running well when suddenly the rand() function that i use started to fail. and i get the error:

> rand();

Error, empty number

also i get many aditional errors in some sentences where i am addressed to some '?' simbols which are supposed to be in my sentendes.

has anyone gone trhough that? any help will be appreciated.

josep

I'm trying to do a least square estimation

with(plots);

q := array([892., 1012., 1060., 987., 680., 739., 809., 1275., 946., 874., 720., 1096.]);

p := array([1.23, 1.15, 1.10, 1.20, 1.35, 1.25, 1.28, .99, 1.22, 1.25, 1.30, 1.05])

lnx := array([seq([ln(p[t])], t = 1 .. 12)]);

lny := array([seq([ln(p[t])], t = 1 .. 12)]);

pointplot({seq([ln(p[t]), ln(q[t])], t = 1 .. 12)}, symbol = circle, axesfont = [TIMES, 14], labels = [x = ln(p), y = ln(q)])

Hi all! I have a list of data. I can use pointplot to plot them. Now, whatshould I do if I want to connect (join) these points toghether like an ellipse or rectangle or others form? For example:

S := [[1,1], [3,1], [4,2], [3,3], [2,3], [1,2]];

thanks  

Hi,

Can i use method=laplace to solve an ode with no initial condition?

ode := diff(phi2(x),`$`(x,2))-Omega0*diff(phi2(x),x)-k*R1*E1/C*sigma*phi2(x)-l^2*phi2(x)+2*R*k/C*N2*exp(Omega0*(x-1))*cosh(l*(x-1))*l*C2/exp(-l) = 0;

bcs:=phi2(1)=0,phi2(S0)=-N4*Phi;

sol := dsolve({ode, bcs}, phi2(x), method=laplace);

Thanks

Good night.

I have a problem with this error "Error, (in unknown) invalid input: `dsolve/numeric/lexorder` expects its 2nd argument, b, to be of type {indexed, name, numeric}, but received cos(t) "

help me please

final-robot-circul.mw

Hey,

I have one function that is consisted of several matrices.. The function is,

R := log(determinant(MCOV))+trace(multiply(SCOV, inverse(MCOV)))-log(det(SCOV))-2+Transpose(SM-TAU-multiply(L,K))&*inverse(MCOV)&*(SM-TAU-multiply (L, K));

where MCOV, SCOV, SM,TAU, L, K are all matrics. In a MCOV and L, there are symbols also..

I have tried to get...

Dear Mapleprimes,

I have a problem with the sum command. I'm differentiating wrt. a value q[i] in a sum. I have the following:

diff(sum((1/2)q[i], i=1..n),q[i]);

This returns:

n(1/2)

but I'm differentiating wrt. q[i] not the whole sum. Any ideas?

Thanks very much.

Christian

Hi, I have 2 sets of data:

P := array([1.23, 1.15, 1.10, 1.20, 1.35, 1.25, 1.28, .99, 1.22, 1.25, 1.30, 1.05]);

Q := array([892, 1012, 1060, 987, 680, 739, 809, 1275, 946, 874, 720, 1096]);

p=P(t), q=Q(t) i.e. both p & q are a function of parameter t  t=1..12

2 functions: 

x=ln(p)

y=ln(q)

I'm trying to display x against y , ie x=ln(p) on the horizontal axis, y=ln(q) on the vertical

Dear Mapleprimes,

I'm trying to add a sequence of numbers using the add command. It appears that it can only add up to a specific number. The following works:

add(2*i, i=1..5)

gives 30.

But it is not possible to do:

add(2*i, i=1..n)

such that n is a parameter.

Does anyone know how to add a finite series of values where n is unknown?

Is there a way to change the default settings for ArrayTools[RandomArray](distribution= )  ?

There are two distribution values available uniform, which is on the unit interval and normal which draws from a normal distribution on the unit interval. 

Can we modify those settings?  Such that using distribution=uniform (or normal) is forced to some user setting outside the unit interval?

Unable to open these maple files, please help

I have a question in Maple TA that is asking for an answer in radians, and when I post the answer that I get it does not accept it...I'm assuming I'm doing the problem correctly, but my answer is not in the correct format.

How to speedup them? There are more than 20 functions that are evaluated one by one. Is option 'remember' + permanent remembered item of pure symbolic calculation can speedup this process? How also efficiently to do simlify itself? Can i actually use more kernels in one session or to paralilize available one?

Hello everyone

I have a function, constructed by numerically solving a set of differential equations.  I need to find a best fit for this function with an analitic model with two parameters. I tried to extract some points of this function and then using nonlinearfit:

xvalues:=Vector([seq(10⁵ ..10⁶,10⁴);

yvalues:=Vector([seq(evalf(function),x=10⁵ ..10⁶,10⁴)]);

with(Statistics):

Hello,

I have a derivation to do for my PhD thesis, and it is long and tedious. It is essentially a case of splitting sums, making substitutions and then simplifying. I believe maple can do this for me, but have not found how yet. Any suggestions would be more than welcome. I have done this for a third order problem (three nested sums) and the derivation runs to many pages. I now need to do so for the 4th order problem, and it is a more than daunting prospect