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

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)')

Answer 1

[Rik]

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)')

[arham zakki edelo]

thanks , can you explain to me about the NaN function

[arham zakki edelo]

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]

@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.

Answer 2

[Praveen Kumar Pakkirisamy]

What was your question and what are you trying to do? It is not quite clear from your Code

[arham zakki edelo]

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]

This is not an answer, but a comment. Please delete this and repost as a comment.