How I should make a loop for coefvct's roots?

Question

Nima Izadyar 2019-8-20

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https://ww2.mathworks.cn/matlabcentral/answers/476944-how-i-should-make-a-loop-for-coefvct-s-roots

回答： Divya Yerraguntla 2019-8-27

采纳的回答： Divya Yerraguntla

I am trying to calculate the following formula using Matlab:

x = 34.704 - 0.34 * 10^-8 * [(x+273)^4-(r+273)^4] + 1.1 * h * (x - T)

h= 2.38 * (x - T) ^ 0.25 , for 2.38 (x - T) ^ 0.25 > 12.1 * u ^ 0.5

h= 12.1 * u ^ 0.5 , for 2.38 (x - T) ^ 0.25 < 12.1 * u ^ 0.5

r = ( (G+273)^4 + 2.5 * 10^8 * u^ 0.6 * (G - T) ) ^ 0.25 - 273

G= 0.5 * r + 0.5 * T

i= 1 : 10, and x= (x1, x2, ..., x 10) , r= (r1, r2, ..., r10), h= (h1, h2, ..., h10), T= (T1, T2, ..., T10), u = (u1, u2, ..., u10), G = (G1, G2, ..., G10)

I am trying to find x, which I reckon I should use coefvct for finding roots, but it is complicated to connect x and other parameters.

It would be much appreciated if you could please advice me regarding this matter.

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Answer 1

Divya Yerraguntla 2019-8-27

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Hi Nima,

It is not always necessary to create a coefficient vector and use roots function to solve a polynomial equation. You could use vpasolve function from Symbolic Math Toolbox, which takes in the entire equation as the input argument. Have a look at this link for more information about vpasolve function.

You can have a look at this question, especially its extended questions in comments to create loops to solve equations with changing variables or variable vectors.

Hope it helps!