How can I add two sets of results with different size?

Hello all,

I have two sets of data which are as follows:

T1:1x4655757 dndT1: 1x4655757,

T2:1x45669 dndT2: 1x45669,

The above results are obtained as a result of solving a differential equation on the same T interval but with two different parameters (two different B):

dndT=a*exp(B/T)*(1-n);

where a and B are constants.

I want to add these two results up (dndT1+dndT2). I don't know how can I do that. Can anyone help me with that.

[Akira Agata]

Questions for clarification:

1. "same T interval" means T1 and T2 cover the same range? (such like T1(end) - T1(1) = T2(end) - T2(1) ?)
2. Another parameter in the equation n is also constant?

[Faezeh Manesh]

Yes, you are right. They cover the same range

Answer 1

[Walter Roberson]

I suggest that when you call ode45 that you pass in a vector of multiple times instead of two times exactly. When you pass two exactly, ode45 reports output whenever it feels like it, which could end up being different number of times for different B values. When you pass a vector of 3 or more times it reports back at those times only. You would then get the same length of results in the output and so would be able to add directly.

[Akira Agata]

Ah, 'dndT' means a differential equation. I got it, thank you !

[Walter Roberson]

"as a result of solving a differential equation" -- it was mentioned in the question ;-)

[Faezeh Manesh]

I solved my differential equation as follows:

Tspan = [294 361];
odefun1 = @(t,x) firstorderDSC1(x,t);
[temp1,n1] = ode45(odefun1, Tspan, 0, options);

Do you mean that I should change my Tspan as follows for example:

Tspan=[294 300 361]

[Walter Roberson]

I suggest linspace(294,361,1e6)

Or possibly more than 1e6. The first one must be oscillating a lot if it feels that it needs 4e6 outputs.

I wonder if you should use ode23s? I suspect that you have a stiff system.

[Faezeh Manesh]

This works well. Thanks a lot.