Need help with subplot

Instructions:

Create a MATLAB function called plot05 that generates a 3x1 matrix of subplots, where yi = sin(x*i*π) appears in the ith subplot and i = 1, 2, 3. Define the length of the guitar string to be an array of 100 equally spaced values over the interval [0, 1]. Plot the first harmonic in subplot 1 and set the linewidth property to 1. Plot the second harmonic in subplot 2 and set the linewidth property to 2. And plot the third harmonic in subplot 3 and set the linewidth property to 3.

so i need to create a subplot that looks like this:

http://i1308.photobucket.com/albums/s617/pingchu93/graph4_zps3c103949.jpg

but my graph is way off--what is wrong with my code?

function [y] = plot05(x,i)
x= 0:.01:1
i= [ 1 2 3]
y = sin (x.' * i .* pi) 

hold on
x = 0:.01:1;
subplot(3,3,1);
linewidth = 1;
plot(x,y,'LineWidth',linewidth)

hold off

hold on

x = 0:0.01:1;
subplot(3,3,4);
linewidth = 2;
plot(x,y,'LineWidth',linewidth)

hold off

hold on

x = 0:0.01:1;
subplot(3,3,7);
linewidth = 3;
plot(x,y,'LineWidth',linewidth)

hold off

Answer 1

[Matt Fig]

x = 0:.01:pi;
subplot(3,1,1)
plot(x,sin(x))
subplot(3,1,2)
plot(x,sin(x*3))
subplot(3,1,3)
plot(x,sin(x*6))

Think of the arguments to SUBPLOT as setting up a grid. You want a 3-by-1 grid, so the first two arguments to subplot should be 3,1. The third argument is which of the axes on that grid you want to create. So when you say subplot(3,1,3) you are asking subplot to create the third axes on a 3-by-1 grid. This lets you do neat things like this:

x = 0:.01:pi;
subplot(3,1,1)
plot(x,sin(x))
subplot(3,1,2)
plot(x,sin(x*pi))
subplot(3,2,5)
plot(x,sin(x*2*pi))
subplot(3,2,6)
plot(x,sin(x*3*pi))

[Ping]

thanks! The lines are a bit different than from the graph but i think I can figure it out from here.

Answer 2

[Wayne King]

Because you want

subplot(3,1,1)

subplot(3,1,2)

and not

subplot(3,3, ...)

subplot(3,3, ) means 3 rows and 3 columns, you just want 3 rows and 1 column

Answer 3

[Image Analyst]

Try this:

x= 0:.01:1
i= [ 1 2 3]
y = sin (x.' * i .* pi) 

hold on
x = 0:.01:1;
subplot(3,3,1:3);
linewidth = 1;
plot(x,y,'LineWidth',linewidth)

x = 0:0.01:1;
subplot(3,3,4:6);
linewidth = 2;
plot(x,y,'LineWidth',linewidth)

x = 0:0.01:1;
subplot(3,3,7:9);
linewidth = 3;
plot(x,y,'LineWidth',linewidth)

% Enlarge figure to full screen.
set(gcf, 'units','normalized','outerposition',[0 0 1 1]);

[Image Analyst]

The key was doing 1:3, 4:6, and 7:9 to get all three slots in the row. Of course you could do subplot(3,1,1) which works okay in this case but sometimes you want to mix things up like have the top plot be three wide and have 6 single wide plots below it. So that's why using a range gives you additional flexibility that you might want to know about, and might need at some point. Also, your "hold" commands were unnecessary.

[Ping]

thanks! I got 3 different subplots just like in the picture. But how do I get 3 separate lines? My 3 graphs all have 3 lines on each plot instead of 1 line per plot.

[Image Analyst]

make i 1, 2, or 3, not an array [1 2 3].