Undefined function 'conv2' for input arguments of type 'sym'.

Question

Fatma Abdullah 2017-6-16

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/345031-undefined-function-conv2-for-input-arguments-of-type-sym

回答： John D'Errico 2017-6-16

im trying to implement the function in the attached image but i get an error at the convolution step saying "Undefined function 'conv2' for input arguments of type 'sym'."

 and my code as follows :
if true
  clc;
close all;
M=8;
N=32;
K=14;
c=2;
p=1;
i=13;
s=1;
syms pfa1 i T
eqn = (symsum(nchoosek(M,i)*(pfa1)^(i)*(1-pfa1)^(M-i), i, s, M)==10^(-6));
solve(eqn,pfa1);
result=solve(eqn,pfa1);
result=double(result);
result=result( result<1 & result>0 & abs(imag(result))<2*eps );
e=result
f_t=p^(c/2).*(c/2)*t.^((c/2)-1).*exp(-(t/p).^(c/2))
F_t=1-exp(-(t/p).^(c/2));
fk_t=K*nchoosek(N/2,K).*(1-F_t).^(N/2-K).*(F_t).^(K-1).*f_t
Fk_t=symsum(nchoosek(N/2,i).*(1-F_t).^(N/2-i).*(F_t).^(i), i, K, N/2)
%fz_t=2.*fk_t.*Fk_t
fz_t=conv(fk_t,fk_t)
q=fz_t.* exp(-(T*t/p).^(c/2))
fun = @(t) q
o=integral(q,0 ,Inf)
%eqn=q==e;
%T=solve(eqn, T,'Real',true)
end

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Answer 1

John D'Errico 2017-6-16

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/345031-undefined-function-conv2-for-input-arguments-of-type-sym#answer_270924

But conv2 is not defined for symbolic input. It was not written for that purpose. Just wanting software to do what you want is rarely going to work. I suppose that is one reason why they have documentation. :)

A convolution is just an integral. You will need to write as such, although the desired integral may or may not have a symbolic solution.