how do i solve invalid data type error?

Hi everyone, i just created a partial function by using piecewise function, and further i wanted to convolute the function with itself and i get the invalid data type error when i do that.I get that i have to convert symbolic function to some numeric argument and i've tried some functions such as sym2cell but it didnt work out.This is the error:

Error using conv2

Invalid data type. First and second arguments must be numeric or logical.

And here is my code below:

a = 10;
b = 4;
syms   t;

r = piecewise(a<t<(a+b),(a+b));

y = conv(r,r);
                                                                                                                                                                            

Answer 1

[Aashray]

Hello Erkut,

The issue you're encountering is because “conv()” function in MATLAB is intended for numerical arrays, not symbolic expressions. And the variable “r” which holds the piecewise function is a symbolic expression.

As far as I know, MATLAB does not directly support convolution for symbolic expressions. So, you will have to perform the convolution manually following the convolution expression:

You may refer to below code for better understanding:

syms t tau;
a = 10;
b = 4;

r = piecewise(a < t < (a + b), (a + b), 0);

% Perform symbolic convolution
conv_result = int(r * subs(r, t, t - tau), tau, -inf, inf); 
disp(conv_result);

Also attaching the documentations of symbolic substitute “subs()” and integration “int()” functions for reference:

• https://www.mathworks.com/help/symbolic/sym.subs.html
• https://www.mathworks.com/help/symbolic/sym.int.html