How to convert a sym variable to an ordinary variable?

Hello, I am trying to convert my code back to ordinary variables so I can use it in signal analyzer. The code is below

close all;
clear all;
clc;

t= linspace(-1,3);
syms x_t(t);
 x_2(t) = piecewise(t<-1,(2),-1<t<=-.5,(t.*4+6),-.5<t<2, (-2.4*t+3),t==2,(2),t>=2, (2));

y = -x_2(-1-t)+1;
y_e=((-x_2(-1-t)+1)+(-x_2(1+t)+1))*.5;
y_o=((-x_2(-1-t)+1)-(-x_2(1+t)+1))*.5;

tiledlayout('flow')

nexttile
fplot(x_2)
title('Original Signal');
xlabel('time'); % label the horizontal (time) axis
ylabel('amplitude'); % label the vertical (x_t) axis

grid on;


nexttile
fplot(y)
title('Transform');
xlabel('time'); % label the horizontal (time) axis
ylabel('amplitude'); % label the vertical (x_t) axis

grid on;


nexttile
fplot(y_e)
title('Even');
xlabel('time'); % label the horizontal (time) axis
ylabel('amplitude'); % label the vertical (x_t) axis

grid on;


nexttile
fplot(y_o)
title('Odd');
xlabel('time'); % label the horizontal (time) axis
ylabel('amplitude'); % label the vertical (x_t) axis

grid on;

Any help is appreciated thank you!

Answer 1

[Walter Roberson]

symbolic variables can be converted to numeric only if they have no unbound variables and all expressions with bound variables (such as int() expressions) converge.

Your y* variables contain the unbound variable t and so cannot be converted to numeric.

However, you can subs() specific numeric values for the unbound variables and try to double() the result. That should work provided the expression converges.

[Roosevelt]

Hi thanks for responding can you give me an example? I am new to matlab

[Walter Roberson]

T = linspace(-1,3);
syms x_t(t);
x_2(t) = piecewise(t<-1,(2),-1<t<=-.5,(t.*4+6),-.5<t<2, (-2.4*t+3),t==2,(2),t>=2, (2));
y = -x_2(-1-t)+1;
y_e=((-x_2(-1-t)+1)+(-x_2(1+t)+1))*.5;
y_o=((-x_2(-1-t)+1)-(-x_2(1+t)+1))*.5;

Y = double(subs(y, t, T));
Y_e = double(subs(y_e, t, T));
Y_o = double(subs(y_o, t, T));
plot(T, Y, T, Y_e, T, Y_o);
legend({'y', 'y_e', 'y_o'});

[Roosevelt]

Thank you! this led me to fix up my code and get a desired result. I really appreciate your help!

Answer 2

[Chunru]

t= linspace(-1,3);
syms x_t(t);
 x_2(t) = piecewise(t<-1,(2),-1<t<=-.5,(t.*4+6),-.5<t<2, (-2.4*t+3),t==2,(2),t>=2, (2));
y = -x_2(-1-t)+1;
y_e=((-x_2(-1-t)+1)+(-x_2(1+t)+1))*.5;
y_o=((-x_2(-1-t)+1)-(-x_2(1+t)+1))*.5;
tiledlayout('flow')
nexttile
fplot(x_2)
title('Original Signal');
xlabel('time'); % label the horizontal (time) axis
ylabel('amplitude'); % label the vertical (x_t) axis
grid on;
nexttile
fplot(y)
title('Transform');
xlabel('time'); % label the horizontal (time) axis
ylabel('amplitude'); % label the vertical (x_t) axis
grid on;
nexttile
fplot(y_e)
title('Even');
xlabel('time'); % label the horizontal (time) axis
ylabel('amplitude'); % label the vertical (x_t) axis
grid on;
nexttile
fplot(y_o)
title('Odd');
xlabel('time'); % label the horizontal (time) axis
ylabel('amplitude'); % label the vertical (x_t) axis
grid on;

whos

  Name        Size            Bytes  Class     Attributes

  cmdout      1x33               66  char                
  t           1x1                 8  sym                 
  x_2         1x1                 8  symfun              
  x_t         1x1                 8  symfun              
  y           1x1                 8  sym                 
  y_e         1x1                 8  sym                 
  y_o         1x1                 8  sym                 

% for example of y_e
y_e = symfun(y_e, t); % convert to symfunction
y_e = double(y_e(-5:.1:5))  % evaluate the function and convert to double

y_e = 1×101

-1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 -1.0000 0.7800 0.6600 0.5400 0.4200 0.3000 0.1800 0.0600 -0.0600 -0.1800

[Roosevelt]

Hello, thanks for responding. Is there a way to keep the graphs the same when doing the conversion?