Questing about symbolic differentiation, inner derivative

Hi everybody,

I am doing a project that requires alot of symbolic differentiation. I need to differentiate expression like cos(theta(t)) w.r.t t, is this possible with matlab? If so, how?

I know that I could easily do this with mathematica but I am also using simulink, so it would be easier just to use one software.

BR,

Per

Answer 1

[Walter Roberson]

Yes, the Symbolic Toolbox can handle that without difficulty. The syntax would go something like

syms theta(t) t
diff(cos(theta(t))

Answer 2

[Per]

Walter,

Thank you for the fast answer. Can I extend this syntax to vectors of symbols?

BR,

Per

[Walter Roberson]

See http://www.mathworks.com/help/symbolic/diff.html

You can differentiate a vector of expressions, but you cannot differentiate with respect to a vector. If what you are looking for is the partial derivatives then you can use the syntax

diff(F,var1,...,varN) differentiates F with respect to the variables var1,...,varN.

but you cannot use diff(f,[var1, var2, var3... varn])

What you can do in MATLAB is

varvec = [var1, var2, var3... varn];         %however it got built
T = num2cell(varvec);     %convert to cell array
diff(F, T{:})

the T{:} syntax expands the cell array to become individual arguments to the call.