How to plot step functions in Matlab

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Sangani Prithvi
Sangani Prithvi 2020-10-31
评论： VBBV 2020-10-31
I have a function involving
y=o for x<o;
y=exp(-x)*cos(x) for 0<x<2pi();
y=2*exp(-x)*cos(x) for x>2pi();
please help me to plot such a type of function in xy space

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采纳的回答

VBBV
VBBV 2020-10-31
编辑：VBBV 2020-10-31
%if true
% code
%end
x = -2*pi:0.1:3*pi;
for i = 1:length(x);
if x(i)<0;
y(i)=0;
elseif x(i)<=2*pi & x(i)>=0 ;
y(i) = exp(-x(i))*cos(x(i)*pi/180);
elseif x(i) > 2*pi ;
y(i) = 100*exp(-x(i))*cos(x(i)*pi/180);
end;
end;
plot(x,y)
axis([-2*pi 3*pi -0.2 1])
  3 个评论
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Sangani Prithvi
Sangani Prithvi 2020-10-31
y(i) = 100*exp(-x(i))*cos(x(i)*pi/180
can you please explain why did you mutliply with 100 in the above equation?
VBBV
VBBV 2020-10-31
you can use a smaller number, say 2, but
y(i) = 2*exp(-x(i))*cos(x(i)*pi/180);
gives a very small step height compared to
y(i) = exp(-x(i))*cos(x(i)*pi/180)
So in the graph it is not noticeable clearly
Thats why i used to 100 which amplifies the step height.
Remember in both cases the step nature does not vary. i,e, decreasing exponential function according to your equations

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更多回答（1 个）

Vladimir Sovkov
Vladimir Sovkov 2020-10-31
编辑：Vladimir Sovkov 2020-10-31
syms x;
y=piecewise(x<0,0, 0<=x<2*pi,exp(-x).*cos(x), x>=2*pi,2*exp(-x).*cos(x));
t=linspace(-pi,4*pi,1000);
plot(t,subs(y,x,t));
  2 个评论
Vladimir Sovkov
Vladimir Sovkov 2020-10-31
Welcome.
By the way, in the question, you did not specify what the function is equal to at the boundary points x=0 and x=2*pi; in the code I implied the right limit but you can easily alter this convention.

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