I am trying to use Optimization[LSSolve] to fit the solution to a differential equations to data. I can solve my problem using Matlab, but I'd like to be able to use Maple as well. This is Maple 10. The proc is not getting the values of the parameters.
> data := [[0,95], [11,425], [22, 928], [33,1358], [44,1589], [56,1683], [67,1724]]:
> try2 := proc(K,alpha,r,IC)
local DE1,R; print(K,alpha,r,IC): # for debugging
DE1:=diff(y(t),t)=r/alpha*y(t)*(1-(y(t)/K)^alpha);
R:=dsolve({DE1,y(0)=IC},numeric);
map((d) -> rhs(R(d[1])[2])-d[2],data):
end:
> sol2 := Optimization[LSSolve](try2(K,alpha,r,IC), initialpoint = {r=.09, K=1750, IC=95, alpha=.3});

Hi,
I have a ‘slight’ problem (you will probably recognize it Joe! :-) ).
It concerns the values of Tau, omega in my worksheet (see below). If I set Tau=0.7, omega=0.7*m*Eta everything is rosy, and works fine. If I start tweaking these values (which I have to) things go a bit pair shaped.
I either get an error message after the first call to dsolve (e.g. when tau=0.5, omega=0.7*m*Eta) :
*"Error, (in dsolve/numeric/checksing) ode system has a removable singularity at r=1. Initial data is restricted to {Phi(r) = .20650095602297*diff(Phi(r),r)+.82088920025557e-1*I*diff(Phi(r),r)}"*

I don't know how much interest this has for people on this forum, but I have just discovered (I think) a difference in how M10 and M11 handle differential equations. I just received M11 late last week, and when I tried to run in M11 a worksheet I had developed in M10 I got an error. It had to do with the fact that M10 gave me 2 solutions to a DE, whereas M11 gave me one. The first solution which M10 gave me was r(theta) = 0. M11 skipped this trivial solution. Arguably this is a better way to go, but it can cause problems for older worksheets, as it did on mine, where my next line tried to parse the second solution of the previous line. I have uploaded a file which illustrates this. Is it possible that there is some setting I could change in M11 to make it give me the same set of solutions as M10 gives?

Hi.
>sol2:=dsolve(
{diff(c(x),x,x)=c(x) , c(0)=5, int(c(x),x=0..1)=3 },c(x));
Error, (in PDEtools/sdsolve) the input system cannot contain equations in the arbitrary parameters alone; found equation: _F1[x]-3
this is a DE of second order, so it requires two conditions to find the constants.. I wanted to give one of the conditions in the form of an integral, but i get the error above.
Any idea why?
thanks

hi guys!
Alright... I have a system of equations in the form of:
y=ux^[v+w*ln(x)]
So this is what I do:
1.Define the function:
h := -> u*x^(v+w*ln(x))
2.Next, I have to tell maple some solutions to this equation:
eqns1 := {h(.6) = 13, h(5) = 120, h(11) = 1000}
3.tell maple to solve:
solve(eqns1, {v, u, w})
But I get:
Warning, solutions may have been lost
and I get no solutions.
What is the problem with what I have input?
Thanks a lot guys!

I got the eigenvalues of the Jacobian matrix of a nonlinear time variant system. One of them is like:
0.5000000000e-2-0.2500000000e-2*y+0.5000000000e-2*x+0.2500000000e-2*sqrt(36.-12.*y-24.*x+y^2-4.*x*y+4.*x^2)
Now I'd like to make x and y still vary with time, i.e.
0.5000000000e-2-0.2500000000e-2*y(t)+0.5000000000e-2*x(t)+0.2500000000e-2*sqrt(36.-12.*y-24.*x(t)+y(t)^2-4.*x(t)*y(t)+4.*x(t)^2)
x(t) and y(t) bear a relation by differential equations.
Any ideas on how I implement this?
Thanks a lot!

February 27 2007
Jinny 8
Hi everyone,
Could you please have a look at my maple file. Im trying to solve a set of 4 differential equations but maple takes ages to solve and doesnot give the answer at the end either. The reason can be that the equations have to high power.
Do you know any other dsolve method I can use or anything I can do to fix this problem?
Thank you very much!
Jinny

View 3868_Pressure drop 2.mw on MapleNet or

Download
Ok, another of my "how do you do this" questions:
In solving a an equations such as:
y''-4*y'+5*y = 0
I would like to show the roots; is there a function that will just pull the roots from the equation as written or do I have to write the equation like:
m^2 + 4*m + 5 = 0
and use:
solve(m^2+4*m+5);
Thanks...

People on this forum have been unbelievably helpful.
I am trying to write some worksheets to help flatten the learning curve for folks who are new to MAPLE. Trouble is, being not far from the newbie stage myself, I may very well be making significant mistakes about the capabilities of MAPLE and thus teaching people cumbersome and inefficient ways of doing things. With that in mind, if anyone has the time to critique the following, I would be most appreciative.

I am having the hardest time plotting the qualitative behavior of the solutions of these differntial equations. I keep getting Error, (in plots/animate) no non-zero vectors found. If someone could walk me through plotting these equations, it would be greatly appreciated.
Equation1: dx/dt=x^2, x(0)=1, 0≤t<>

February 21 2007
derio 40
My goal is to obtain a formula F:= x -> fa(x)*c1_1(x)+ fb(x)*c1_2(x)+fc(x)*c2_1(x)+... where every ci_j(x) is a function of x. fa, fb, fc are known functions of x. I do not need to have it printed, I just need it to return a numerical value for every value of x I throw in.
I have obtained the solutions of ci_j's in the form
Sol[1]:=[c1_1=f11(x), c1_2=f12(x), c1_3=f13(x), ...], N1 terms
Sol[2]:=[c2_1=f21(x,c1_j’), c2_2=f22(x,c1_j’), c2_3=f23(x,c1_j’), ...], N2 terms
Sol[3]:=[c3_1=f31(x,c1_j’,c2_j’), c3_2=f32(x,c1_j’,c2_j’), c3_3=f33(x,c1_j’,c2_j’), ...], N3 terms
Sol[4]:=[c4_1=f41(x,c1_j’,c2_j’,c3_j’), c4_2=f42(x,c1_j’,c2_j’,c3_j’), c4_3=f43(x,c1_j’,c2_j’,c3_j’), ...], N4 terms

Dear Sir:
I try to solve a set of simultaneous equations.
But, it is not easy to get a solution by using
MAPLE package.
restart;
eq1:=P-2*P*cos(w*t[2])+(P+1)*cos(w*t[3])=0;
eq2:=-2*P*sin(w*t[2])+(P+1)*sin(w*t[3])=0;
_EnvAllSolutions:=true: _EnvExplicit:=true:
solve({eq1,eq2},{t[2],t[3]});
But, MAPLE does not give me what I want.
I expect that the solution should be in
the following way:
t[2]=(1/w)*arccos((4*P^2-2*P-1)/(4*P^2));
t[3]=(1/w)*arccos((2*P^2-2*P-1)/(2*P^2+2*P));
where w and P are positive constants.
Could you help me to get the solution?
Thanks

February 16 2007
Nasos 84
Hi,
I have three equations Y=f(t) with each equation corresponding to a probability as shown below.
Y1=f(t) with probability of 0.05%
Y2=f(t) with probability of 5% and
Y3=f(t) with probability of 50%
If we assume that these probabilities belong to a normal distribution how can I work out the equations for 99.95% and 95%probability.In other words I would like to mirror Y1 and Y2.
The idea is to plot all the equations of 0.05%,5%,50%,95% and 99.95% probability in the same plot and create a 3D surface where the axis will be Y,t and P(probability) or even better generate the equation of P=f(Y,t) that will describe this surface.

how do I solve differential equations with maple V?