When I run this code I get empty strings for when setting a range for vpasolve, when I do not set the range I only get one solution, even with random on. The range is set so that it does include the one solution matlab gives me, x=2, y=0 and b=1.5. for the range I've tried -Inf Inf and NaN NaN, to have it try all numbers. So please do not give me the answer of saying that my system has no solution, it clearly does. It also won't solve it symbolicly (same issue with solve), while I can give 1 possible solution. 0.5*(x+y)=1, b*(x+y)=3 ---> x+y=2 and b=1.5
So something else must be wrong, I would appreciate it if you let me know what I'm doing wrong here.
clear all; %just to be safe syms x y b a=0.5; somevalue=1; someothervalue=3; eq1= a*x+a*y == somevalue; %this is your first equation eq2= b*x+b*y == someothervalue; %this is your 2nd equation eqs=[eq1,eq2]; %use this for vpasolve and set range in range vars=[x,y,b]; %these are the variable you want to solve for range = [-1 3; -2 5; -Inf Inf]; %NaN means you set no range
%you can use solve or vpasolve, second one being numeric, which is the one you'll probably want sol=zeros(5,3); for i = 1:5 temp1 = vpasolve(eqs, vars, range, 'random', true); temp = solve(eqs, vars); sol(i,1) = temp.x; sol(i,2) = temp.y; sol(i,3) = temp.b; end sol temp1.x temp1.y temp1.b
Now I have another clear problem/error when using the solve option, obviously the answer here should be 9:
syms x eq12 = -3 == sqrt(x); solve(eq12) ans = Empty sym: 0-by-1
sqrt(x) is short-hand for x^(1/2) . 9^(1/2) only refers to the primary square root, not to all square roots. Work-around:
>> syms A >> solve(A==sqrt(x),x) ans = A^2 >> subs(ans,A,-3) ans = 9