# User Portlet

Discussions |
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Thanks Roland! That worked! |

Thanks Marco, however interpolation does not give me an analytic function, as Piecewise does. |

But I meant how to calculate the number of infected over a specified period of time, say t=0 to t=10 with your model. |

Hi, I am trying to set up a code to plot a streamplot from the results from a SIR model. The problem to solve is **r′=F(r)** where r=(x,y) and F(x,y)=(−b*x*y/n,b*x*y/n−k*y) and where b=3.3925; k=2.95; n=157759; How can I set up... |

Hi, I have the given command sol = Flatten[DSolve[y'[x] == y[x]^3/x^3 + y[x]/x + 1, y[x], x]] which yields the solution Solve[ArcTan[(-1 + (2 y[x])/x)/Sqrt[3]]/Sqrt[3] + 1/3 Log[1 + y[x]/x] - 1/6 Log[1 - y[x]/x + y[x]^2/x^2]... |

As written in the discussion, this problem is there *what ever the coefficients are*. In your case they give 0=0. If you change them, they don't give this equality, and still it doesn't solve. Try this: c=3*10^8 T=2 h=1.0545718*... |

Hello, I would like to solve the following PDE for Psi(x,y,z,t) ![enter image description here][1] [1]: https://community.wolfram.com//c/portal/getImageAttachment?filename=Screenshotfrom2021-08-2615-21-55.png&userId=967554 where alpha,... |

Thanks for that, it show now the function, but the plot is still blank. |

PS: The interval of the plot is a little bit large. It is the absolute center which is important. How do I"zoom" in on the center? |

Hello, I have a a polar function given by: u[r_, phi_, n_] := Piecewise[{{BesselJ[1.5 r, n]*Exp[I n phi], 0 1}}] u0[r_, phi_, k_] := Sum[I^(-n) BesselJ[n, r] Exp[I n phi], {k, -5, 5}]; u1[r_, phi_, n_] := ... |