Getting error about index in for loop

%for loop for plotting given data
for k = 0:size(dataN)
    val = dataN(:,k);
    avg = mean(val);
end

I am getting this error:

Index in position 2 is invalid. Array indices must be positive integers or logical values.

Error in Lab5_Problem2 (line 25)
    val = dataN(:,k);

I cannot figure out why, but I am trying to extract the first row of the array (dataN). Thank you for any help!

Answer 1

[per isakson]

Three problems:

• replace 0:size(dataN) by 1:size(dataN,2). Matlab's indexing is one-based.
• avg = mean(val); overwrites avg in every iteration; only the last value will persist
• "trying to extract the first row of the array (dataN)" dataN(:,k) refers to the k:th column

[Carly Hudson]

How do I make it so avg is not overwritten every iteration? I think I am trying to refer to the kth coulmn because I am trying to extract the average from every column of data. Sorry if any of this is wrong, but I am very new to MatLab. Thank you for your help!

[per isakson]

This should do it

wid = size(dataN,2);
avg = nan( 1, wid ); 
for k = 1 : wid
    val = dataN(:,k);
    avg(k) = mean(val);
end