Plotting y=x^n in MATLAB with Loops

[fball558]

anyone know MATLAB?

Homework Statement

Using Matlab, write an m-file that creates subplots of y=x^n for n=[1:6] and
x = [-10:0.01:10]. Each subplot needs appropriate labels in bold and using superscripts. this should also be commanded from within a loop and using num2str commands where necessary.

The Attempt at a Solution

i started out with a nested for loop as followed.

for x = [-10:0.01:10]
for n=[1:6]
y=x^n
plot(y) trying to just graph what I am getting so far in the loop
end
end


when i run the program i get just a blank graph??
any help would be great!

 

[MATLABdude]

Homework Statement

Using Matlab, write an m-file that creates subplots of y=x^n for n=[1:6] and
x = [-10:0.01:10]. Each subplot needs appropriate labels in bold and using superscripts. this should also be commanded from within a loop and using num2str commands where necessary.

The Attempt at a Solution

i started out with a nested for loop as followed.

for x = [-10:0.01:10]
   for n=[1:6]
      y=x^n
      plot(y)          [b]%[/b]trying to just graph what I am getting so far in the loop
    end
end

when i run the program i get just a blank graph??
any help would be great!

Well, the beauty of MATLAB is that you can run operations on vectors and arrays, and don't have to do element-wise operations (most of the time), as you might in C or C++ (or whatever your intro computing course was).

So, you could do something like the following:

x=[0:0.01:10]
y=x.^1     %note the period before the ^, this tells MATLAB to raise each element of x to the power of 1

plot(y,x)
pause(1)     %pauses a second

y=x.^2
plot(y,x)

Now, you could pack each of your y-vectors into a 2-D matrix (array), and sort things out later, or you can use a cell array (the curly braces), and store the vectors separately.

x=[0:0.1:10];
for n=1:6
     y{n}=x+1;
end
plot(x,y{1}, x,y{2}, x,y{3}, x,y{4}, x,y{5}, x,y{6})

BTW, a great way to find what MATLAB functions do is just to type 'help' and the name of the function, for instance:
>> help plot

...which brings up the help file for the Plot function. More in-depth documentation is available at the MATLAB website (I found this invaluable when I was a MATLAB programmer one summer--bookmark the top page!):
http://www.mathworks.com/access/helpdesk/help/techdoc/ref/arithmeticoperators.html

 

[Mene]

Hello, thank you for sharing your attempt at solving this problem. I would suggest breaking down the problem into smaller steps and checking for errors along the way.

First, let's focus on creating a single subplot for a specific value of n. We can use the "hold on" command to plot multiple curves on the same figure. So, our code for a single subplot would look something like this:

x = [-10:0.01:10]; % define x values
n = 2; % choose a specific value of n
y = x.^n; % calculate y values
plot(x, y) % plot the curve
xlabel('x') % add x label
ylabel(['y = x^', num2str(n)]) % add y label with superscript using num2str

Next, we can use a for loop to create subplots for different values of n. We can also use the "subplot" command to specify the position of each subplot. So, our updated code would look like this:

x = [-10:0.01:10]; % define x values
figure % create a new figure
for n = 1:6 % loop through values of n
y = x.^n; % calculate y values
subplot(2,3,n) % create subplot at position n
plot(x, y) % plot the curve
xlabel('x') % add x label
ylabel(['y = x^', num2str(n)]) % add y label with superscript using num2str
end

I would also recommend checking for errors along the way, such as making sure the "hold on" command is included and checking the syntax of the "subplot" command. Additionally, you can use the "disp" command to print out the values of x and y at each iteration of the loop to make sure they are correct.

I hope this helps and good luck with your further attempts!