Error using sym/subsindex
显示 更早的评论
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!
2 个评论
Stijn Haenen
2020-8-7
编辑：Stijn Haenen
2020-8-7
There is no symbolic variable as input for symsum. You do h(k), but what does this mean, k had not a value yet so you cannot take the k th element of h. And you didn't define tau so tau(k) does not exist. And you should use length(h) instead of size, i think.
If you have a function of h expressed in k you can solve your problem, i dont know if you can without a function for h.
this line works, but h is excluded from it:
sym_sum_ans=(1/(a(i)^(1/2)))*((t_max - t_min)./(size(t)-1))*symsum(wav((k-ttt(j))/a(i)), 1, length(h)-1);
num_ans=vpa(sym_sum_ans)
Viktoriia Buliuk
2020-8-11
采纳的回答
Walter Roberson
2020-8-8
0 个投票
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.
更多回答（1 个）
KSSV
2020-8-7
Initialize the cell first.
Q =cell(length(a),length(ttt)) ; % initialize
USe this in the loop.
Q{i,j} = %% your formula with syms
3 个评论
Viktoriia Buliuk
2020-8-7
KSSV
2020-8-7
Check the spelling.....it should be length
Viktoriia Buliuk
2020-8-7
编辑：Viktoriia Buliuk
2020-8-7
类别
在 帮助中心 和 File Exchange 中查找有关 Calculus 的更多信息
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
