Trying to plot function

Hey, so ihave been asked to plot this function
I found a way to do this
syms x
y=piecewise(x<-4, 0, -4<=x<3, x+2, x>=3, x-2);
fplot(y)
and i get this graph
Now, when i try another way to do this
i get this graph
this is the code
t = linspace(1,1000,1000); %%time
X1=@(t) (t<=-4).*0+(t>=-4 & t<3).*(t+2)+(t>=3).*(t-2);
subplot(2,2,1)
plot (t,X1(t))
axis([-6 6 -20 20]);
Im trying to understand why this way (the second graph) doesnt work.
Thnx.

4 个评论

well for one thing, in the second instance you are defining you x-coordinates as going from 1 to 1000, so no, you wont have anything plotted below x=1
I need 1000 points in the graph between -6<t<6
also, i'm confused, can you tell me which point on you plot is incorrect?
are you aware that you are plotting only integer X values and the line is just connecting the dot's

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 采纳的回答

You were mislead by two factors:
  1. You were not using the same plotting range for both of them
  2. You were sampling at a low number of points the conditionals but not for piecewise
t = -6:6; %%time
X1=@(t) (t<=-4).*0+(t>=-4 & t<3).*(t+2)+(t>=3).*(t-2);
subplot(2,2,1)
plot(t,X1(t))
axis([-6 6 -20 20]);
title('discrete using conditionals')
subplot(2,2,2)
fplot(X1, [-6 6]);
axis([-6 6 -20 20]);
title('continuous using conditionals')
syms x
y(x) = piecewise(x<-4, 0, -4<=x<3, x+2, x>=3, x-2);
subplot(2,2,3)
plot(t, y(t))
axis([-6 6 -20 20])
title('discrete using piecewise')
subplot(2,2,4)
fplot(y, [-6 6])
axis([-6 6 -20 20])
title('continuous using piecewise')

3 个评论

Ok i understand thank you.
Nut now i have another problem becuase i changed the range.
For some reason i get this problem: Array indices must be positive integers or logical values.
at the plot line.
Y1=X1(t).*(t-1);
subplot(2,2,3)
plot(t,Y1(t))
axis([-6 6 -20 20]);
grid on
title('Subplot 1: Y1')
thanks you!

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