Which function can be used?

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adrooney 2014-10-5

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https://ww2.mathworks.cn/matlabcentral/answers/157456-which-function-can-be-used

评论： adrooney 2014-10-5

采纳的回答： adrooney

I have a function dA/dt= k(2-2.374A)/2.12

can I use ode45 here?

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Answer 1

adrooney 2014-10-5

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https://ww2.mathworks.cn/matlabcentral/answers/157456-which-function-can-be-used#answer_154006

编辑：Jan 2014-10-5

在 MATLAB Online 中打开

Thanks for the answer, also If I have a quadratic expression on the rhs will this work. I tried to write like this. will this work too?

X=zeros (1,1000);
time =0:0.05:50;
k=0.095;
for i=2:1000
  X(i) = (k*(0.305*X(i-1)^2)-(0.554X(i-1))+0.249)*0.05)+X(i-1);
end
plot (time,X)
hold on
plot(time25, alpha25)
end

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Jan 2014-10-5

I've formatted the code.

I guess there is a missing * in "0.554X".

I do not see a connection to the original question - where is teh ODE45 call?

adrooney 2014-10-5

I'll explain you the actual problem. There is function dX/dt = k*f1(t)*f2(t) I substituted the equations of f1 and f2 and ended up with an quadratic equation. dX/dt = k*((0.305*X^2)-(0.554*X)+0.249)

now I need to extrapolate X with different values of time t. I used a for loop to extrapolate with increments of 0.05hr. So how should I approach the problem and I wrote the above code for the values of extrapolated values of X. Now when I run the code it says error in using plot. vector length must be equal. I don't know how to resolve this. Please help me with this and it would be of great help .:) Thank you

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