Replace a syms command

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Sarah Gomez
Sarah Gomez on 11 Feb 2022
Answered: Robert U on 11 Feb 2022
clear;
clc;
syms 'j'
y1 = 7 .* (-0.2).*j.*cos(7.*j + 3);
y2 = 5 .* exp(-1.1).*j.*tan(3.*j - 1);
fplot(y1, [0 30]);
hold on;
fplot(y2, [0 30]);
title({'Graph'})
xlim([0 30]);
ylim([-6 6]);
xlabel('Time, t(s)');
ylabel('Amplitude y1, y2 (mm)');
legend('y1(t) = 63^(-0.2)tsin(7t+3)', 'y2(t) = 4e^(-0.1)tsin(3t-1)');
saveas(gcf, 'Graph.png');
I'm trying to replace the syms 'j' command with numerical values for x that would replace the j's in my functions. I can't seem to get the same graph with what I've tried.

Answers (1)

Robert U
Robert U on 11 Feb 2022
Hi Sarah Gomez,
I am not quite sure whether I understood you question correctly, but removing the syms j command is not sufficient since "j" is pre-defined as imaginary unit.
If you want to get rid of the symbolic representation, you can use anonymous functions. That would allow you to keep the rest of the code.
Your legend does not represent your used formulae correctly, that is why you could have a look at func2str().
clear;
clc;
y1 =@(x) 7 .* (-0.2).*x.*cos(7.*x + 3);
y2 =@(x) 5 .* exp(-1.1).*x.*tan(3.*x - 1);
fplot(y1, [0 30]);
hold on;
fplot(y2, [0 30]);
title({'Graph'})
xlim([0 30]);
ylim([-6 6]);
xlabel('Time, t(s)');
ylabel('Amplitude y1, y2 (mm)');
legend(func2str(y1),...
func2str(y2),'FontSize',12);
Kind regards,
Robert

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