Partial derivative of a time derivative

Hello,

I have the following code:

syms('qxy(t)',[2,1]); qxy = formula(qxy);
u1 = formula(qxy);
u1_dot = formula(diff(u1,t)); 
T = diff(u1_dot(1),diff(qxy1(t), t));

Here I create a symbolic u1 with qxy1(t) and qxy2(t).

Then I take the derivative wrt time of u1 to get u1_dot, with elements diff(qxy1(t), t) and diff(qxy2(t), t).

Now I want to take the partial derivative of u1 wrt diff(qxy1(t), t) and diff(qxy2(t), t)

So in formula form for u1_dot(1):

But if I run this code, I get an error instead of the value 1.

Does someone know how to solve this?

Thanks!

[Prabhan Purwar]

Hey,

Kindly mention the error you are facing.

Thanks

[Tobias]

Hi, thank you for your comment!

Luckily I already resolved this problem by updating to version 2020b.

This wasn't possible in the 2019 version of Matlab.

Thanks!

[Prabhan Purwar]

Glad to know that the issue is resolved.

Answer 1

[VBBV]

I don't get any error It shows the result as T = 1 as you mentioned.

%if true
  % code
% end
syms('qxy(t)',[2,1]); qxy = formula(qxy);
u1 = formula(qxy);
u1_dot = formula(diff(u1,t)); 
T = diff(u1_dot(1),diff(qxy1(t), t));
>>
T =
1

[Tobias]

Hi,

Thanks for your reply!

I was using version 2019b, but I found out that it actually works since version 2020b.

So updating did the trick for me