# problem with taking Differentiate from variable with counter !

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shahin hashemi on 25 Apr 2018
dear all
i need to write a code that have x symbolic variable that contain x=[x1 x2 x3 .... xn] and also x is depended to variable t (time).at last i want to Differentiate from x. for 3 or 4 x it is easy to write code like below :
>> syms x1(t) x2(t) x3(t)
>> x=[x1 x2 x3]
x(t) =
[ x1(t), x2(t), x3(t)]
>> diff(x,t)
ans(t) =
[ diff(x1(t), t), diff(x2(t), t), diff(x3(t), t)]
now when i want to write code that contain 30 x it is difficult to this in this way
i also try this but it doesnt work :
>> syms t
>> x(t) = sym('x%d',[1 4])
x(t) =
[ x1, x2, x3, x4]
>> diff(x,t)
ans(t) =
[ 0, 0, 0, 0]
is there any way to do this in this way and if it is i also need a way to call the specific x
for example :
for i=1:3
for j=1:3
xij(t)=...
end
end
i know writing in this way is wrong but just for clearing my idea i really appreciated if someone could help me

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