How to start at 0?

For this assignment I have to start at 0, this means that when I plot the figure, it has to start at 0 and end at 30. With the code that I wrote, it starts at 1 and ends at 31 when I plot it. How can I fix this?

x=zeros(31,1);
y=zeros(31,1);
i=0;

for i = 0:30;
    if i == 0
        x((i+1),1)= sum(sum(M));
        y((i+1),1)= 0;
        i = i+1;
    else
        [M,l]=k(M);
        x((i+1),1)=sum(sum(M));         
        y((i+1),1)=l;              
        i=i+1;
    end
end

[Geoff Hayes]

Anna - the code you have written start at i equal to zero. Isn't that what you want, or is there a problem when you run the above code?

I noticed that M isn't defined before you enter the for loop so that will cause a problem. What is the initial value of M?

Also, you may want to consider renaming your indexing variable i to k since MATLAB uses both i and j to represent the imaginary number.

[Anna]

Hi! Yes I wrote it that way but it doesn't show when I plot it.

I will show you the whole code that I wrote :). Thank you for the tip, but my assignment demands me to use variable k.

Mycode=[0 4 9 5 4 7 2];  

M = m(My); 

x=zeros(31,1);
y=zeros(31,1);
i=0;

for i = 0:30;
    if i == 0
        x((i+1),1)= sum(sum(M));
        y((i+1),1)= 0;
        i = i+1;
    else
        [M,l]=k(M);
        x((i+1),1)=sum(sum(M));        
        y((i+1),1)=l;              
        i=i+1;
    end
end
x;
y;
M;

[Geoff Hayes]

Anna - what is the code that you are using to plot the data? Is it x versus y or something else? Since x is just the sum of all elements in the matrix M then it won't necessarily start at zero...

As an aside, you can simplify the double sum of M to simply

 x((i+1),1) = sum(M(:));

[Anna]

Geoff, This is the code that I use to plot the data:

figure('name', 'E.jpg', 'NumberTitle', 'off'); 
bar(x,'b');               
hold on                    
plot (y,'-ro');             
xlabel('T(dags)');  
ylabel('A');           
grid on                     
axis ([-5 35 0 10000])

Answer 1

[Geoff Hayes]

Anna - if you wish to plot the first element of y against zero, and each subsequent value at 1,2,3,... then just do the following

 plot(0:length(y)-1,y,'ro');

which will plot all elements of y against values of "x" (this isn't your x but the x-axis) from 0 to 30.

Try the above and see what happens!