How to write Subscript in MATLAB?

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

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.

[KALYAN ACHARJYA]

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]

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.

Answer 1

[Bhomik Kankaria]

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

[Ankitha Pai]

Thanks alot for the relpy.

Currently using y(k-i) works for me. And yes live editor is helping.

[ALFIE NELSON]

Is there any way to create subscripts in the regulat editor and not the live editor? Or is there a way to publish on the live editor?

Answer 2

[Steven Lord]

You don't need to explicitly create so many symbolic variables.

d = sym('d', [1 10])

d = 

y = sym('y', [1 2])

y = 

syms u_k a_i
A = [0.2867, -0.2428];
B = [0.6607 , -0.2732];
d(1) = 1;
v = d*u_k.^(1:10).'

v = 

Now work with v, d(someNumber), and y(someNumber) instead of trying to dynamically create variable names d_1, d_2, etc.

Answer 3

[Yasmine]

Y_mean