How substitute variable in Matlab? -


i have trouble set of equations. have: 

x' = f(t, x, u) - it's set of equations - dimension n x1' = .. x2' = .. x3' = ..

and have u - it's vector (u1, u2, u3..)

how can substitute u in set of equations? example :

x1' = sin(t) * u1 + sin(u2) x2' = u2*x2  u1 = sin(1000t) u2 = cos(1000t)

and need 

x1' = sin(t) * sin(1000t) + sin(cos(1000t))            x2' = cos(1000t) * x2

thank's.

well, assuming using symbolic toolbox:

syms t u1 u2 x2; x1prime = sin(t) * u1 + sin(u2); x2prime = u2 * x2;

then can use method or b. method a:

x1prime = subs(x1prime, [u1 u2], [sin(1000*t) cos(1000*t)]) x2prime = subs(x2prime, u2, cos(1000*t))

method b:

u1 = sin(1000*t); u2 = cos(1000*t); x1prime = subs(x1prime) x2prime = subs(x2prime)

i tested both methods on matlab r2011a. use works best you.


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