How to write Subscript in MATLAB?

Question

Ankitha Pai 2021-2-24

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/754534-how-to-write-subscript-in-matlab

回答： Yasmine 2023-2-22

Hello, So in my code i need to have subcripts in order to have multiple values of that varibale. I used the format given in matlab documents but still hvaing error

syms d_1 d_2 d_3 d_4 d_5 d_6 d_7 d_8 d_9 d_10 u_k a_i y_k y_(k-i)

A = [0.2867, -0.2428];

B = [0.6607 , -0.2732];

d_1 = 1;

v_k = d_1*u_k+d_2*u_k^2+d_3*u_k^3+d_4*u_k^4+d_5*u_k^5+d_6*u_k^6+d_7*u_k^7+d_8*u_k^8+d_9*u_k^9+d_10*u_k^10;

%yk formula

for k = 1:2

for i = 1:10

x = a_i*y_(k-i)

z = b_i(u_(k-i)+symsum(d_p*u^p(k-i),2, 10))

y_k = -x +z

end

Please help me out and let me know if the declaration of syms and the other varibales is wrong and how to correct it.

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KALYAN ACHARJYA 2021-2-24

编辑：KALYAN ACHARJYA 2021-2-24

Problem is here y_(k-i) what exactly are you trying to do? Is it sys variable or sym function.

You can use y(k,i) as sym function directly.

Ankitha Pai 2021-3-16

it is system variable. So basically i have the y(k) values those are the outputs and y(k-i) will be the past outputs so using for loop i needed to go through the data set and get the value.

Right now writing it like y(k-i) works well for me and i used live editor

Thankss for you help.

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Answer 1

Bhomik Kankaria 2021-2-27

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https://ww2.mathworks.cn/matlabcentral/answers/754534-how-to-write-subscript-in-matlab#answer_634764

Hi Ankitha,

Currently, MATLAB Live Editor displays symbolic variables with subscripts, superscripts, and accents in standard mathematical notation.

Hence you need to use live scripts to use the subscript functionality. Also live editor does not support naming the variable as y_(k-i) and will throw an error. You can use name like y_k_i etc. depending on the use case.

To see more examples of the variable names refer the below link-

https://www.mathworks.com/help/symbolic/add-suffixes-to-symbolic-results.html