solve an equation using solve() produces an array instead of a unique value

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jojo 2019-11-17

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https://ww2.mathworks.cn/matlabcentral/answers/491594-solve-an-equation-using-solve-produces-an-array-instead-of-a-unique-value

评论： Star Strider 2019-11-18

采纳的回答： Star Strider

d = 32*h + 200*(32*h - 8)*((4*h - 1)^2 - 1) - 16

I am trying to solve for h using "solve(d,h)" , however, I keep getting an array for of solutions!

[1/2

1/8 - (7*2^(1/2))/80

(7*2^(1/2))/80 + 1/8 ]

How could I obtain a unique value for h? The solution does not seem right. Is there a better function to be used ?

Thanks.

采纳的回答

Star Strider 2019-11-17

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/491594-solve-an-equation-using-solve-produces-an-array-instead-of-a-unique-value#answer_401951

在 MATLAB Online 中打开

The result is correct. There are three roots.

Plot it to see the result:

syms h 
d = 32*h + 200*(32*h - 8)*((4*h - 1)^2 - 1) - 16;
ds = solve(d)
figure
fplot(d, [-0.1 0.6])
hold on
plot(ds, zeros(size(ds)), 'pg')
hold off
grid

I did not post them initially. I was just explaining that 'h' is to be assigned to some x and y parameters that take singular values. Is there a way of writing x and y such that they can take both single digits and arrays size of h? like x(:,3) something like that. I am knew to matlab and I do not fully grasp array slicing and indexing yet. Thanks.