Hi everyone,

I want to draw a phase portrait of a particle to see it moving but I don't want to see its trajectory. I don't know how to explain, here is what I did:

restart;with(DEtools), with(plots), with(linalg):

g11:=1;g21:=g11;

z:=exp(I*((t/(2*Pi))+(Pi*j)));

f1:=evalc(Re((I/(2*Pi))*((g11/(subs(j=1,z)-(x(t)+I*y(t))))+(g21/(subs(j=2,z)-(x(t)+I*y(t)))))));

q1:=evalc(-1*Im((I/(2*Pi))*((g11/(subs(j=1,z)-(x(t)+I*y(t...

Hi everyone,

I have a problem with DEplot.

Here is the code:

restart;with(DEtools), with(plots), with(linalg):

z:=exp(I*((t/(2*Pi))+(2*Pi*j/3)));

f1:=Re((I/(2*Pi))((1/(subs(j=1,z)-(x(t)+I*y(t))))+(1/(subs(j=2,z)-(x(t)+I*y(t))))+(1/(subs(j=3,z)-(x(t)+I*y(t))))));

g1:=-1*Im((I/(2*Pi))((1/(subs(j=1,z)-(x(t)+I*y(t))))+(1/(subs(j=2,z)-(x(t)+I*y(t))))+(1/(subs(j=3,z)-(x(t)+I*y(t))))));

sys1:=[diff(x(t),t)=f1,diff(y(t),t)=g1]:

Hi everyone,

I have this differential equations:

gamma1:=1;gamma2:=1;

l:=t->sqrt((x1(t)-x2(t))**2+(y1(t)-y2(t))**2);
2 2
l := t -> sqrt((x1(t) - x2(t)) + (y1(t) - y2(t)) )

DE:=[diff(x1(t),t)=(-1/(2*Pi))*gamma2*(y1(t)-y2(t))/l(t),diff(y1(t),t)=(-1/(2*Pi))*gamma1*(x1(t)-x2(t))/l(t),diff(x2(t),t)=(-1/(2*Pi))*gamma2*(y2(t)-y1(t))/l(t),diff(y2(t),t)=(-1/(2*Pi))*gamma1*(x2(t)-x1(t))/l(t)]:

I want to draw the phase portraits (x1(t...

Hi everyone,

Here is the code:

Ralpha:=sqrt(d)*IdentityMatrix(2):

alpha:=Array([WienerProcess(Ralpha),WienerProcess(Ralpha),WienerProcess(Ralpha),WienerProcess(Ralpha)]):

alpha1:=k->Vector[column]([[alpha[1](k)[1]],[alpha[1](k)[2]],[alpha[2](k)[1]],[alpha[2](k)[2]],[alpha[3](k)[1]],[alpha[3](k)[2]],[alpha[4](k)[1]],[alpha[4](k)[2]]]):

Finance[ExpectedValue](alpha1(0)[1]*alpha1(0)[1],timesteps=100,replications=10^4);

----> 

Hi everyone,

Working on my project, I have this error "Error, (in VectorCalculus:--) too many levels of recursion".

The project is about filetring a stochastic process.

When I want to calculate one of the integrals, I have that error.

Here is the code:

Rxi:=sqrt(d)*IdentityMatrix(4):

xi:=WienerProcess(Rxi);

Reta:=sqrt(d)*IdentityMatrix(2):
eta:=Array([WienerProcess(Reta...