how to plot y=ax+b for different equations

How to plot a line for different equations for the x and y, for example: y=1 when 0<x<=1; y=2x+1 when 1<x<=3; y=-2x-1 when 3<x<=5; y=0 when x>5

Answer 1

[Titus Edelhofer]

Hi Vivi,

• set up a vector x between 0 and 1
• compute y
• plot y vs. x
• hold on
• do the same for the interval [1 3]

Titus

[Vivi]

is that use'if' fuction to set up X?

[Titus Edelhofer]

Not really. You can either compute one vector for plotting like Iain did, or plot the different pieces separately using "hold on" in between.

Answer 2

[Iain]

 x = min_desired_x:step_size:max_desired_x;
 y = (x>0 & x<=1) * 1 + ...
     (x>1 & x<=3) * (2*x+1) + ...
     (x>3 & x<=5) * -(2*x+1) + ...
     (x>5       ) * 0;
 plot(x,y)

[Titus Edelhofer]

You will need to use

(x>0 & x<=1) .* 1

and likewise for the other terms. Note the ".*" instead of "*".