Substitute an array of number for a symbolic variable

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David Arnold
David Arnold 2012-11-1
评论： Walter Roberson 2019-7-12
Hi,
I have:
syms x y
f=x^3+y^3+3x^2+2y^2+9
fx=diff(f,x)
now, I'd like to substitute these two vectors of x and y values into the expression fx.
x=[1,2,3,4,5]
y=[6,7,8,9,10]
How do I do that with the subs command? If I can't do that with the subs command, what do you recommend?
David.
  1 个评论
Star Strider
Star Strider 2012-11-1
编辑：Star Strider 2012-11-1
Question: Do you want a matrix with the function evaluation of fx for each value of (x,y) as an individual element?
What version of MATLAB do you have? Beginning with 2012a, symbolic functions are possible.

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采纳的回答

Walter Roberson
Walter Roberson 2012-11-1
subs(fx, {x, y}, {[1,2,4,5,6}, [6,7,8,9,10]})
This syntax is documented relatively far down in the examples.

更多回答（1 个）

Azzi Abdelmalek
Azzi Abdelmalek 2012-11-1
syms x y
f=x^3+y^3+3*x^2+2*y^2+9
fx=diff(f,x)
x=[1,2,3,4,5]
y=[6,7,8,9,10]
eval(f)
eval(fx)

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