MATLAB: Error using sym/subsindex

symsum

Hello!
I got the following mistake:
Error using sym/subsindex (line 836)
Invalid indexing or function definition. Indexing must follow MATLAB indexing. Function arguments must be symbolic variables, and function body must be sym
expression.
Error in examp (line 22)
Q(i,j) = (1/(a(i)^(1/2)))* ((t_max – t_min)./(size(t)-1))*symsum(h(k)*wavelet((tau(k)-ttt(j))/a(i)),k, 1, size(h)-1);
The code is following:
type Ez_dry.csv;
Test = importdata('Ez_dry.csv');
t = Test(:, 1);
h = Test(:, 2);
 
t_max = max(t);
t_min = min(t);
 
wav = @(tau)(2/(3.^(1/2)*pi^(1/4))*exp(-tau.^2/2).*(1 - tau.^2));
 
ttt = t_min:0.1*10^-10:t_max;
 
a = 0.3*10^-10:0.6*10^-11:10^-9;
 
for i = 1:length(a) 
for j = 1:length(ttt)
    syms k 
    Q(i,j) = (1/(a(i)^(1/2)))*((t_max - t_min)./(size(t)-1))*symsum(h(k)*wav((tau(k)-ttt(j))/a(i)),k, 1, size(h)-1);
end
end
S = real(Q);
figure(2);
contour (ttt, 1./a, S, 500)
Could you, please, help me to find a solution. Thank you in advance!

Best Answer

symbolic variables can never be used as indices. You cannot symsum or symprod and use the control variable as an index.
Instead you need to produce the definite vector of individual values and sum() or prod() that.
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