Unable to perform assignment because brace indexing is not supported for variables of this type.

Hi everyone, I am trying to run this code:

    clear all
    close all
    clc

    syms x(t) y(t) z(t) A B C D E FF G H I J K LL MM N O P Q R S

    eqn1 = diff(x(t),t) ==  1/ A * ((B * C - B * x(t))) - (x(t) * D * E - FF*((y(t) * z(t)^2)/(z(t)^2 + G * z(t) + G * H))) / ((1/I) + 1/(J * (((K*(FF* x(t) * D * E - ((y(t) * z(t)^2)/(z(t)^2 + G * z(t) + G*H))))) + LL * (((G * FF *  x(t) * D * E/z(t)) - ((y(t) * G * z(t))/(z(t)^2 + G * z(t) + G*H)))) + MM * ((((G * H *FF* x(t) * D * E/z(t)^2) - ((y(t) * G * H)/(z(t)^2 + G * z(t) + G*H))))))) / (K * (FF * x(t) * D * E - ((y(t) * z(t)^2)/(z(t)^2 + G * z(t) + G*H)))));

    eqn2 = diff(y(t),t) == (x(t) * D * E - FF*((y(t) * z(t)^2)/(z(t)^2 + G * z(t) + G*H))) / ((1/I) + 1/(J * (((K*(FF* x(t) * D * E - ((y(t) * z(t)^2)/(z(t)^2 + G * z(t) + G * H)) ) + LL * (((G * FF *  x(t) * D * E/z(t)) - (( y(t) * G * z(t))/(z(t)^2 + G * z(t) + G*H)))) + MM * ((((G * H * FF * x(t) * D * E / z(t)^2) - ((y(t) * G * H)/(z(t)^2 + G * z(t) + G * H))))))/ (K * (FF * x(t) * D * E - (( y(t) * z(t)^2)/(z(t)^2 + G * z(t) + G * H)))))))  - 0.162 * exp(-5153/E) * (((N * (( y(t) * G * H)/(z(t)^2 + G * z(t) + G*H)))/O) - 1)^2 * (P / ((N * (((y(t) * G * H)/(z(t)^2 + G * z(t) + G * H))))) / O));  

    eqn3 = z(t) + 2 * N - ((y(t) * G * z(t))/(z(t)^2 + G * z(t) + G*H))  -  2 * (( y(t) * G * H)/(z(t)^2 + G * z(t) + G*H)) - ((N * Q * z(t))/(z(t)^2 + Q * z(t) + Q*R))  -  2 * ((N * Q * R)/(z(t)^2 + Q * z(t) + Q*R)) - S/z(t) == 0;

    eqns = [eqn1 eqn2 eqn3];

    vars = [x(t); y(t); z(t)];

    origVars = length(vars);

    M = incidenceMatrix(eqns, vars);

    [eqns, vars] = reduceDifferentialOrder(eqns, vars);

    isLowIndexDAE(eqns,vars);

    f = daeFunction(eqns,vars, A, B, C, D, E, FF, G, H, I, J, K, LL, MM, N, O, P, Q, R, S);

    A = 1.5e-6;   
    B = 1.66667e-5;  
    C = 6.51332e-2;  
    D = 8.314;    
    E = 323.15; 
    FF = 149;      
    G = 6.24;  
    H = 5.68e-5; 
    I = 4.14e-6; 
    J = 7.25E-2; 
    K = 2.98e-9;         
    LL = 2.35e-9;     
    MM = 1.69e-9;   
    N = 8;
    O = 1.07e-7;
    P = 10;
    Q = 1.7e-3 ;
    R = 6.55e-8;
    S = 5.3e-8 ;

    F = @(t, Y, YP) f(t, Y, YP, A, B, C, D, E, FF, G, H, I, J, K, LL, MM, N,O, P, Q, R, S);

    vars;
    y0est = [4.58E-02; 1.58; 1];
    yp0est = zeros(3,1);
    opt = odeset('RelTol', 10.0^(-7), 'AbsTol' , 10.0^(-7));
    [y0, yp0] = decic(F, 0, y0est, [], yp0est, [], opt);
    [tSol,ySol] = ode15i(F, [6720, 27840], y0, yp0, opt);
    for k = 1:origVars
      S{k} = char(vars(k));
    end

However, I get the error message:

    Unable to perform assignment because brace indexing is not supported for variables of this type.

    Error in Example01Sept2018 (line 57)
      S{k} = char(vars(k));

The Debugging points me to:

for k = 1:origVars
  S{k} = char(vars(k));
end

When I change to:

    for k = 1:origVars
      S(k) = char(vars(k));
    end

I get an error message:

    Unable to perform assignment because the left and right sides have a different number of elements.

    Error in Example01Sept2018 (line 57)
      S(k) = char(vars(k));

What can I do?

[NN]

i also got the same error ,

Unable to perform assignment because brace indexing is not supported for variables of this type.

do not know how to solve this.Please help

y=xlsread('DelhiTRAIN2.xlsx');
XTrain=y((1:end),1:5);
YTrain=y((1:end),6);


m = min([XTrain(:)],[],2);
M = max([XTrain(:)],[],2);
idxConstant = M == m;

for i = 1:numel(XTrain)
    XTrain{i}(idxConstant,:) = [];
end

[Walter Roberson]

m = min([XTrain(:)],[],2);

The (:) forces a column vector. Why are you asking for the min() along the second dimension for something that is a column vector? The result is just going to be the same as XTrain(:)

 XTrain{i}(idxConstant,:) = [];

The first output of xlsread() is never a cell array, so y() indexed will not be a cell array, so XTrain will not be a cell array, so you should not be assigning into XTrain{i}

What is your purpose in that loop?

Answer 1

[Walter Roberson]

You have

S = 5.3e-8 ;

but later you want to use S to store the names of the variables. I do not recommend re-using the name of a numeric coefficient for something completely different: it gets too confusing.

But if it is for some reason very important to use the name S in both cases, then you will need to assign something to change S into a cell array, such as

S = cell(origVars, 1);

Or you can skip the initialization and the explicit loop and use

S = arrayfun(@char, vars, 'uniform', 0);

[Dursman Mchabe]

Oops! I forgot to change it to SS, I initially intended to change it to SS. Sorry Walter.

[Dursman Mchabe]

Thanks a lot Walter, the code runs perfect with SS.