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# can not plot the graph and there is samething wrong on my script, can anyone checkit

1 view (last 30 days)
arham zakki edelo on 9 Mar 2019
Closed: MATLAB Answer Bot on 20 Aug 2021
clear all
clc
t = [-5:50]
for n =1:length(t)
if (n>=-5&&n<=0);
y1=zeros;
elseif (n>=0&&n<=8) ;
y2=10*n.^2-5*n;
elseif (n>=8&&n<=16);
y3=624-5*n;
elseif (n>=16&&n<=26);
y4=36*n+12*(n-16)^2;
else (n>=26&&n<=50);
y5=2136*exp(-0.1*(n-26));
end
end
figure(1)
plot(n,y1,n,y2,n,y3,n,y4,n,y5)
xlabel('time');ylabel('v(t)')

Rik on 9 Mar 2019
Your code doesn't do what you think it does. You could see that by looking at your variables: they have become scalars, instead of vectors.
What you should do is take advantage of the array processing you can do with Matlab (with logical indexing), or use indexing in your loop.
t = [-5:50]
y = NaN(size(t))
L= t>=-5 & t<=0;
y(L)=0;
L=t>=0 & n<=8;
y(L)=10*t(L).^2-5*t(L);
L=t>=8 & t<=16;
y(L)=624-5*t(L);
L=t>=16 & t<=26;
y(L)=36*t(L)+12*(t(L)-16)^2;
L=t>=26 & t<=50;
y(L)=2136*exp(-0.1*(t(L)-26));
figure(1)
plot(t,y)
xlabel('time');ylabel('v(t)')
##### 3 CommentsShow 1 older commentHide 1 older comment
arham zakki edelo on 9 Mar 2019
and if i want to make 'for if' function to my problems , can you help me to solve that base on my problem
Star Strider on 9 Mar 2019
@arham zakki edelo — Rik’s code uses ‘logical indexing’, the most efficient way to do this problem.
If you want to continue with your for loop and if block, try this:
t = -5:50;
for n =1:length(t)
if (t(n)>=-5&t(n)<=0);
y1(n)=zeros;
t1(n) = t(n);
elseif (t(n)>=0&t(n)<=8);
y2(n)=10*n.^2-5*t(n);
t2(n) = t(n);
elseif (t(n)>=8&t(n)<=16);
y3(n)=624-5*t(n);
t3(n) = t(n);
elseif (t(n)>=16&t(n)<=26);
y4(n)=36*n+12*(t(n)-16)^2;
t4(n) = t(n);
else (t(n)>=26&t(n)<=50);
y5(n)=2136*exp(-0.1*(t(n)-26));
t5(n) = t(n);
end
end
figure(1)
plot(t1,y1, t2(t2>0),y2(t2>0), t3(t3>0),y3(t3>0), t4(t4>0),y4(t4>0), t5(t5>0),y5(t5>0))
xlabel('time')
ylabel('v(t)')
Then go back and un-accept the Comment that you accepted as an Answer, and accept Rik’s Answer that actually provided you with working code.
Experiment to get the result you want.

What was your question and what are you trying to do? It is not quite clear from your Code
##### 2 CommentsShow NoneHide None
arham zakki edelo on 9 Mar 2019
i want to make a plotting picewise graph from these function which is the interval time is -5 to 50 second, please help me
Rik on 9 Mar 2019
This is not an answer, but a comment. Please delete this and repost as a comment.

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