Single ODE solved with ODE45
显示 更早的评论
wspan = 0:0.01:10000;
x0 = 0;
[w,x] = ode45(@(w,x) (0.012528*(1-(9.8*10^(-5)*w))*(1.5-x)*(1-x))/(45*(1+16.68...
*(1-(9.8*10^(-5)*w))^(0.5)*x+12.456*(1-(9.8*10^(-5)*w))^(0.5)*(1-x))),wspan, x0);
plot(w,x,'-o');
I wrote the simple code above with the hope to replicate a graph that I obtained from excel. However, the range of x on the vertical axis in the MATLAB plot are way smaller than what I've expected. Could someone please explain to me how to fix it such that it matches my excel plot. (the excel plot is proven to be correct) Thanks, much appreciated. Attached (Excel Plot & MATLAB Plot)
3 个评论
Star Strider
2017-10-14
What is the original differential equation?
Jan
2017-10-14
Note: 9.8*10^(-5) is a multiplication and an expensive power operation in every call of the function, while 9.8e-5 is a cheap constant. SQRT(x) is much faster than x^0.5. Runtime is not your problem here, but it is worth to keep this in mind.
Star Strider's idea is obviously right: If the output by Excel is proven to be correct, and the Matlab code does not produce the same result, the Matlab code contains a different formula. We cannot fix it without seeing the correct formula.
Michelle Zhou
2017-10-16
回答（1 个）
David Goodmanson
2017-10-16
编辑：David Goodmanson
2017-10-19
0 个投票
Hi Michelle,
Looks like your constant of .012528 is off by a factor of 10, should be .12528. Once that change is made, there is good agreement with the excel plot.
类别
在 帮助中心 和 File Exchange 中查找有关 Ordinary Differential Equations 的更多信息
2017-10-14
2017-10-19
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
