ive tried doing it but i dont know why the plot is not right t=-2:0.1:2; if t<=-1 y=-5.*t-5; elseif t<0 y=t.^2+1; elseif t<1 y=pi.^t; elseif t>=1 y=pi+sin(pi

[Stephen23]

https://web.archive.org/web/20211231053555/https://www.mathworks.com/matlabcentral/answers/1619770-ive-tried-doing-it-but-i-dont-know-why-the-plot-is-not-right-t-2-0-1-2-if-t-1-y-5-t-5-e

Answer 1

[David Hill]

t=-2:.1:2;
f=zeros(size(t));
f(t<=-1)=-5*(t(t<=-1))-5;
f(t>-1&t<0)=t(t>-1&t<0).^2+1;
f(t>=0&t<1)=pi.^(t(t>=0&t<1));
f(t>=1)=pi+sin(pi*t(t>=1));
plot(t,f);

[Colty Day]

uhm...sorry is there other way on doing it... what if i use if elseif

[Image Analyst]

David we normally don't give full solutions to what is obviously his homework. Colty, I know you accepted this but beware of turning it in. I know for a fact that some professors use "plagiarism detectors" and you don't want to get caught turning in someone else's solution as your own.

It looks like you actually wanted a version using if/else and I gave you hints for that and you almost got it except that t on the right hand side needed to be t(k).

Answer 2

[Image Analyst]

How do I get help on homework questions on MATLAB Answers? - MATLAB Answers - MATLAB Central

Hint to get you started

function f(t)
ft = zeros(1, length(t));
for k = 1 : length(t)
    if t(k) <= -1
        ft(k) = 
    elseif
    end
end
plot(t, ft, 'b-')

[Colty Day]

uhm... i put function there but wont work

t=-2:0.1:2;
y= zeros(1, length(t));
for k = 1 : length(t)
    if t(k)<=-1
        y=-5.*t-5;
    elseif t(k)<0
        y=t.^2+1;
    elseif t(k)<1
        y=pi.^t;
    elseif t(k)>=1
        y=pi+sin(pi.*t);
    end
end
plot(t,y,'r-');

[Steven Lord]

You use one element of t in your if conditions but then you write to all of y in the body of the if statement. [You're actually overwriting y with that statement.]

if t(k)<=-1
     y=-5.*t-5;

Did you want to assign to one element of y just like you referenced one element of t?

[Colty Day]

yes , is it possible??? function didnt works in my matlab

[Colty Day]

t=-2:0.1:2;
yt = zeros(1, length(t));
for k =1: length(t)
    if t(k)<=-1
        yt(k)=-5.*t-5;
    elseif t(k)<0
        yt(k)=t.^2+1;
    elseif t(k)<1
        yt(k)=pi.^t;
    elseif t(k)>=1
        yt(k)=pi+sin(pi.*t);
    end
end
plot(t,yt,'r-');

[Image Analyst]

@Colty Day, you almost got it, but you need to use t(k), not the entire t vector, on the right hand side of the equation. If it works for you can you at least "Vote" for this answer. 🙂

t=-2:0.1:2;
yt = zeros(1, length(t));
for k = 1: length(t)
    if t(k) <= -1
        yt(k) = -5.*t(k)-5;
    elseif t(k) < 0
        yt(k) = t(k).^2+1;
    elseif t(k) < 1
        yt(k) = pi.^t(k);
    elseif t(k) >= 1
        yt(k) = pi + sin(pi.*t(k));
    end
end
plot(t,yt,'r-');
grid on;