use vector as input

I want to give each input of a vector as an argument to my function to recive a list of values that i can then plot (my goal is to plot the time it takes to execute the function for a given n). The problem is, that i only get the output of the first entry of the vector. What did I do wrong?

>> n = [1:1:10];
>> [a,b] = calcEulerSum2 (n)

it returns only calcEulerSum2(1)

function [e, a] = calcEulerSum2(n)
den = 1;
e = 1;
tic
 for i = 1 : n
     den = den * i;
     e = e + 1/den;
 end
 a = toc;
end

[dpb]

"What did I do wrong?"

We dunno and have no way to know -- you forgot to show us the code for calcEulerSum2

[dpb]

What do you expect for output and what is the expected input?

I think you aren't using for as documented/wanted here.

Try at the command line to see what you get for:

n=1:3; 
for i=1:n, disp(i), end

followed by

for i=n, disp(i), end

and see if that doesn't clear up the mystery.

Answer 1

[Robert U]

Hi Vincent Degonda,

Your for-loop call is not providing what you expected. Your input variable is a vector already. dpb tried to lead you to that. Output in vector form would need an indexing of your output variable.

function [e, a] = calcEulerSum2(n)
    den = 1;
    e = 1;
    tic
    for i = n
        den = den * i;
        e(end+1) = e(end) + 1/den;
    end
    a = toc;
end

Kind regards,

Robert

Answer 2

[Steven Lord]

So you want to compute the value of e and the time required to compute that value for each element of n? A couple of suggestions:

function [e, a] = calcEulerSum2(n)
den = 1;
e = 1;

Make the variable e an array of ones the same size as n. The documentation page for ones include a couple of examples that you can use as a model.

tic

Before you start timing, you'll need a loop over the elements of the input. Use the numel function that gives the number of elements in an array for this loop.

for whichElement = <you fill this in> % I added this to your code

Continuing on with the code you already wrote:

 for i = 1 : n

You don't want to use the whole n array here, just one element. Which element should you use instead of n here? I think you can guess.

     den = den * i;
     e = e + 1/den;

Since e is now an array here, not just one value, you need to operate on and assign back into a particular element. Which element of e? It should be clear.

By the way, you'll need to adjust how (or more precisely where/when) you initialize den. If the first element of n was 3, what should den be when you start processing the second element of n and what will it actually be?

 end
 a = toc;
end

Since I added a for loop to your code, you'll need one more end statement. Where should the for loop I added end?