How do I plot this?? "if, elseif, else"

t=0;

for i=0:50

    t=t+1

if (0 <= t && t < 10)

    v=(11*(t.^2))-(5*t)

elseif(10 <= t && t <20)

    v=1100-(5*t)

elseif(20 <= t && t <30)

    v=(50*t) + 2*((t-20)^2)

elseif (t >= 30)

    v=1520* exp(-0.2*(t-30))

else

    v=0

end

end

%% After I hit run I get a bunch of numbers. I want to plot these values (v vs t).

[Adam]

You need to store them in an array. This is the most basic part of Matlab and is covered under the 'Getting Started' section when you open the help.

Once you have your arrays then

doc plot

will show you that you can plot them with

plot( t, v )

or, better

plot( hAxes, v, t )

where hAxes is an axes handle you have created from e.g.

figure; hAxes = gca;

Answer 1

[Pawel Jastrzebski]

Firstly,

I think that your first loop overwrites the t value instead of creating a vector of t values.

For what you're trying to achieve, consider the following code:

t = 0:50;

% to plot 't' vs 'v' you need the equal amount of
% datapoints in both vectors

v = zeros(1,length(t));

% Use logical vector to meet your condtions

condition1 = (0<=t & t <10);
v(condition1) = 11*(t(condition1).^2) - 5*t(condition1);

condition2 = (10<=t & t<20);
v(condition2) = 1100-5*t(condition2);

% etc.

% plotting

figure
plot(t,v,'ro--');

[Guillaume]

Yes, while it is possible to create v in a loop, it is much simpler to do it the way Pawel is showing, using logical masks.

[Phi Tran]

thank you