Unrecognized function or variable 't'.

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Dimitrios Samaras 2022-2-28

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https://ww2.mathworks.cn/matlabcentral/answers/1660590-unrecognized-function-or-variable-t

评论： Walter Roberson 2022-3-2

采纳的回答： John D'Errico

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Hello, I'm trying to run the following code,which I found in a paper, but I came up with the following problem

"Unrecognized function or variable 't'."

What should I do in order to fix the problem?

I attach to you the code:

global D1 D2 D3 Ci L
D1 = 10^-10; %cm^2/s
D2 = 10^-6;
D3 = 10^-5;
Ci = 1; % 1 micromolar
L = .001; %200 microns
for n = 0:200
    for i = 1:length(t)
        for j = 1:length(x)
            c1(i,j) = c1(i,j)+2/L*Ci*cos((2*n+1)*pi*x(j)/(2*L))*exp(-D1*((2*n+1)*pi/(2*L))^2*t(i));
        end
    end
end
c1 = c1/c1(1,1); %scaling to account for infinite value at c1(0,0)
figure
mesh(x,t,c1)
% Az -12 El -6
xlabel('x - Distance(m)')
ylabel('t - Time(s)')
zlabel('c(x,t) - Concentration (M)')
title('Analytical Solution')
pAn1 = c1(5,:);
pAn2 = c1(15,:);
pAn3 = c1(35,:);
pAn4 = c1(75,:);
pAn5 = c1(105,:);
figure
plot(x,pAn1,'b',x,pAn2,'g',x,pAn3,'r',x,pAn4,'m',x,pAn5,'k')
xlabel('x - Distance(m)')
ylabel('c(x,t) - Concentration (M)')
xlim([0 0.0001])
title('Analytical solution at distinct times')
legend('t = .5 s','t = 1.5 s','t = 3.5 s','t = 7.5 s','t = 10.5 s')

Unrecognized function or variable 't'.

Thank you very much for your help, in advance

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Torsten 2022-2-28

After you repair the code by supplying a vector t, the same error message will come up with the vector x.

You must supply both x and t to get a plot of the solution of the PDE your infinite series represents.

Dimitrios Samaras 2022-3-1

Thank you very much for your help.

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采纳的回答

John D'Errico 2022-2-28

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1660590-unrecognized-function-or-variable-t#answer_906555

编辑：John D'Errico 2022-2-28

Contact the authors of the paper, as apparently having submitted crap for code with undefined variables. Worse, it got accepted for publication. SIGH. Such is life. Remember that code, completely by itself and out of context, means absolutely nothing.

t is undefined. We cannot guess what they intended by the variable t. (It seems to be a vector.) And since we don't even see the paper itself, how would we guess at what t should mean?

Ok, wait, I'll check the MATLAB crystall ball (it looks a lot like a snow globe.) It is cloudy for a minute, then it tells me t is the letter after s. When I press it yet more, I see it also comes before u. I hope that helps. It you want more clarity than that, I can check the MATLAB tarot cards, but all they ever tell me is I will either soon come into a large inheritance, or my relatives will come into a large inheritance. I am hoping it is not the latter.

Seriously, t is unknown. You should have the paper in hand, so you could actually read the paper and see how the code reflects what is in the paper. We have only the MATLAB crystal ball.