Error: Unable to perform assignment because the left and right sides have a different number of elements.(line 25)
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Asir Tushar
on 28 Mar 2019
Commented: Asir Tushar
on 30 Mar 2019
%chebyshev differentiation matrix
function [D,x] = cheb(N)
if N==0,D=0;x=1;return,end
x=cos(pi*(0:N)/N)';
c=[2;ones(N-1,1);2].*(-1).^(0:N)';
X=repmat(x,1,N+1);
dX=X-X';
D=(c*(1./c)')./(dX+(eye(N+1)));
D=D-diag(sum(D'));
end
%Differentiatio matrix and initial data
N=20;
[D,x]=cheb(N);
D2=D^2;
eps=1;
dt=min([.01,50*N^(-4)/eps]);
t=0;
sigma=.10;
r=.12; K=100;
k=2*r/sigma^2;
v=max(exp((k+1)/2)*x-exp((k-1)/2)*x,0);
t=0;
%Differentition matrix and initial data;
%solve pde
tmax=100;tplot=2
nplots=round(tmax/tplot)
plotgap=round(tplot/dt),dt=tplot/plotgap
xx=-1:.025:1; vv=polyval(polyfit(x,v,N),xx);
plotdata=[vv;zeros(nplots,length(xx))]; tdata=t;
for i=1:nplots
for n=1:plotgap
t=t+dt;v=v+dt*(eps*D2*v);
v(1)=exp(((k+1)/2)*x+(((k-1)/2).^2+k)*t)-exp(((k-1)/2)*x+(((k-1)/2)^2)*t);
v(end)=0;
end
vv=polyval(polyfit(x,v,N),xx);
plotdata(i+1,:)=vv;tdata=[tdata;t];
end
clf,subplot('position',[.1 .4 .8 .5])
mesh(xx,tdata,plotdata),grid on
axis([-1 1 0 tmax -1 2]),
view(-60,55),colormap([0 0 0]),xlabel x,ylabel t,zlabel u
2 Comments
Walter Roberson
on 28 Mar 2019
Which cheb() function are you using?
.. We need to know in order to figure out what the size of D and x will be.
Accepted Answer
Walter Roberson
on 29 Mar 2019
Your x is a column vector of length N+1. You use all of it in the right hand side of your calculation of v(1) so the right hand side is going to have N+1 elements. You will not be able to fit that into the scalar location v(1).
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