Wrong vaules gotten for solving a differential equation after Matlab ODE45!

I run the following code to calculate dy/dT values, however, I found it gave wrong values (~6.3907232e+08) compared to use excel computed values (less than 0.03)

In excel, I simply input y and T values into equation and calculate all dy/dT values. Can you tell me what is wrong in my code? How to get the correct values for differential equation.

equation: dy/dT= a*exp(-b/T)*y.^c*(1-y).^d

clear
tspan=[360,456];​
y0=0.000002;​
a=30000000;b=8000;c=0.6;d=1.35;​
f=@(T,y)(a*exp(-b/T)*y.^c*(1-y).^d);​
[T,y]=ode45(f,tspan,y0);​
data=[T,y];​
dy=f(T,y);
data=[T,y,dy];

[darova]

I used your code

Answer 1

[Jingbo Wu]

I need to calculte plot(T, dy), the plot (T,y) seems to be fine.

I need to calculate dy=dy/dT value.

thanks

Answer 2

[Jingbo Wu]

the plot you posted is plot(T,y)

Answer 3

[darova]

You forgout about point here

[James Tursa]

And also c*(1-y) part needs to be c.*(1-y)

[Jingbo Wu]

thanks for your answers,

I add all points.

f=@(T,y) a.*exp(-b./T).*y.^c.*(1-y).^d;

it generated a 45x45 Matrix ?

Do you know what is wrong? thanks

[James Tursa]

What generated a 45x45 matrix?

Typically, this can result from using a row and a column vector in an operation. The fix is to make them all row vectors or all column vectors. E.g.,

>> row = 1:5;
>> col = row';
>> row.*col
ans =
     1     2     3     4     5
     2     4     6     8    10
     3     6     9    12    15
     4     8    12    16    20
     5    10    15    20    25
>> row.*row
ans =
     1     4     9    16    25
>> col.*col
ans =
     1
     4
     9
    16
    25

[Jingbo Wu]

the resulting of dy is a 45x45 matrix, it should be a 45x1 matrix

thanks