Plot u vs. t with PDEPE. "Index exceeds matrix dimensions."

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Jennifer Yang 2018-8-10

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评论： Torsten 2018-8-16

在 MATLAB Online 中打开

Hello,

I can't seem to figure out how to plot u (concentration) vs. t (time) at a specific x (distance).

function simple_time_dependent_pdepe
    clear all; close all; clc;
    %
    D_ij = 1*10^-6; %Diffusion coefficient D (3.0*10^-7 cm^2/s -> 30 um^2/s)
    L0 = 1; %c0 [nM]
    x_f =0.02; %Length of domain [um]
    maxt = 10; %Max simulation time [s]
    %
    m = 0; %Parameter corresponding to the symmetry of the problem
    x = linspace(0,x_f,100); %xmesh
    t = linspace(0,maxt,100); %tspan
    %
    sol = pdepe(m,@DiffusionPDEfun,@DiffusionICfun,@DiffusionBCfun,x,t,[]);
    u = sol;
    %
    % Plotting
    plot(t,sol(:,500),'LineWidth',2)
      function [c,f,s] = DiffusionPDEfun(x,t,u,dudx)
          D = D_ij;
          %
          %Rate constants
          k_1 = 0.25;
          R_L = -k_1.*u;
          %
          % PDE
          c = 1;
          f = D_ij.*dudx;
          s = R_L;
      end
      %
      function u0 = DiffusionICfun(x)
          u0 = 0;
      end
      %
      function [pl,ql,pr,qr] = DiffusionBCfun(xl,ul,xr,ur,t)
          c0 = L0;
          pl = ul-c0;
          ql = 0;
          pr = 0;
          qr = 1;
      end
  end

I tried using

plot(t,sol(:,500),'LineWidth',2)
However, I get the error "Index exceeds matrix dimensions."

Am I missing something?

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Jennifer Yang 2018-8-15

I'm confused how to go about making the size the same so that I can plot sol vs. time at x = 500

Torsten 2018-8-16

在 MATLAB Online 中打开

plot (t,sol(:,100,1))

plots the solution over time at x(100), e.g.

Does that help ?

Best wishes

Torsten.

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