# Problem with symbolic math

2 views (last 30 days)
Amit Kumar on 21 Oct 2013
Answered: Azzi Abdelmalek on 21 Oct 2013
Hello, I am trying hard to get code running, however I am stuck at a place. Please help me.
I have declared 3 symbolic variables x1,x2,x3. gr is a column vector and function of x1,x2,x3. p1 is a column vector of constants. I want to substitute values of x2,x2,x3 by first, second, and row of p1. That is x1 = 957/2500, x2=-293/1250, etc. And I want to make it as a new vector gr2. MATLAB is giving errors of inconsistent dimensions. Please help! Thanks
syms x1 x2 x3
gr =
2*x1 + 2*x2
2*x1 + 4*x2 + 2*x3
2*x2 + 4*x3
p1 =
957/2500
-293/1250
371/5000
gr2=subs(gr,[x1,x2,x3],[p1(1),p1(2),p1(3)]);

Azzi Abdelmalek on 21 Oct 2013
syms x1 x2 x3
gr =[2*x1 + 2*x2;2*x1 + 4*x2 + 2*x3; 2*x2 + 4*x3]
p1 =[957/2500;-293/1250;371/5000];
gr2=subs(gr,{x1,x2,x3},{p1(1),p1(2),p1(3)})

sixwwwwww on 21 Oct 2013
Edited: sixwwwwww on 21 Oct 2013
Dear Amit, it is working fine:
syms x1 x2 x3
gr = [2*x1 + 2*x2; 2*x1 + 4*x2 + 2*x3; 2*x2 + 4*x3];
p1 = [957/2500; -293/1250; 371/5000];
gr2 = subs(gr,[x1,x2,x3],[p1(1),p1(2),p1(3)]);

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