How to create a graph time vs value n

Hello,

I have a function that we enter a value n. Next I designed a matrix here and it measures time (tic,toc) until vector returns result.

Now I want to produce a graph for 4<=n<=50 vs time, How can this created?

Thanks for the helpers :)

function [A,VectorOut,B]= pp(n)
tic

f=4*ones(1,n^2);
m=diag(f);
x = zeros(1,n^2);
x_new = x;

j=0;
while j~=n^2
    [m(j+1,j+2)]=-1;
    [m(j+1,j+4)]=-1;
    [m(j+2,j+1)]=-1;
    [m(j+4,j+1)]=-1;
    j=j+1 ;
end
t=m(1:n^2,1:n^2);

v=zeros(1,n^2);
v(1)=1;
v(n^2)=1;

A=t;
B=v';

    for i = 1:n^2
        x_new(i) = (B(i) - sum(A(i,1:i-1).*x_new(1:i-1)) - sum(A(i,i+1:n).*x(i+1:n)))/A(i,i);
    end
      
VectorOut=x_new'
toc
end

Answer 1

[Ameer Hamza]

I think it might be better if you move the tic ... toc lines outside the function. For example, remove these lines and then run the following code

n = 4:50;
ts = zeros(size(n));
for i = 1:numel(n)
    tic
    [A,VectorOut,B]= pp(n(i));
    ts(i) = toc;
end
plot(n, ts)

Alternatively, you will need to return the value of 't' too. For example,

function [A,VectorOut,B,t]= pp(n)
tic

f=4*ones(1,n^2);
.. ..
.. ..
.. ..
.. ..
.. .. 
VectorOut=x_new'
t = toc
end

and then run the code

n = 4:50;
ts = zeros(size(n));
for i = 1:numel(n)
    [A,VectorOut,B,ts(i)]= pp(n(i));
end
plot(n, ts)

[Emilia]

Thank you :)

Answer 2

[Deepak Gupta]

Hi Emilia,

Placed of toc in the function will just display the elapsed time there instead you need to return the elapsed time from this function, to the script where you will be called this function. i.e. in your function you can write.

totalTime = toc;

And then return it.

In your script you need to save these times with respect to n values. i.e.

n = 4:50;
totalTime = zeros(1, size(n));
for n
    [~, ~, ~, nTime] = pp(n);
    totalTime(n-3) = nTime;
end

Now you can plot time vs n.

plot(totalTime, n)

Hope this helps,

Cheers,

Deepak

[Emilia]

Thank you :)