How to pass integers in a loop using MATLAB - matlab

Question

I am trying to run the following code:
%% Getting Stocks
stocks = hist_stock_data('01012013','07112014','GDXJ', 'SPY','GOOGL', 'QQQ', 'AAPL');
%% Loop to get the stocks in order by date
while i <= 5
stocks(1,i).Date=datenum(stocks(1,i).Date);
stocks(1,i).Date = stocks(1,i).Date(end:-1:1);
stocks(1,i).AdjClose = stocks(1,i).AdjClose(end:-1:1);
stocks(1,i).Ticker =stocks(1,i).AdjClose;
end
However I am getting the following error:
Subscript indices must either be real positive integers or logicals.
I have searched the web but do not really understand why I am getting this error?

Answer 1

First off, you must have mentioned that hist_stock_data is a function that you got from an external source and isn't a MATLAB builtin function or variable. Well, I googled for it and found it on MATLAB File Exchange.
Next up looking at the code, here's some advice - Try to avoid using i as an iterator because when uninitialized MATLAB would consider it as the imaginary unit. Read more about it here. That's why you were getting that error - Subscript indices must either be real positive integers or logicals., because the index being used was the imaginary unit that can't be used as an index.
So, we could change i to something like ii -
while ii <= 2
stocks(1,ii).Date=datenum(stocks(1,ii).Date);
stocks(1,ii).Date = stocks(1,ii).Date(end:-1:1);
stocks(1,ii).AdjClose = stocks(1,ii).AdjClose(end:-1:1);
stocks(1,ii).Tiicker =stocks(1,ii).AdjClose;
end
Then, we run the code and see this error -
Undefined function or variable 'ii'.
Now, I made some guesswork and replaced that while-loop with a for-loop that iterates for all the elements in the struct stocks. So, it becomes -
for ii = 1:numel(stocks)
stocks(1,ii).Date=datenum(stocks(1,ii).Date);
stocks(1,ii).Date = stocks(1,ii).Date(end:-1:1);
stocks(1,ii).AdjClose = stocks(1,ii).AdjClose(end:-1:1);
stocks(1,ii).Tiicker =stocks(1,ii).AdjClose;
end
This runs fine, but make sure the results are what you were looking to have in stocks.
If you were looking to run the loop for the first 5 elements only, then do this -
for ii = 1:5