MATLAB: Array weirdness

Question

Hello everyone, I have something very strange happening that I don't understand…

I'm using a for loop to fill an array with values, the first iteration works just fine, the second works correctly but 16 blank rows appear before my second iteration is written. The blank cells have the same number of columns as the first and second. It's only between the first and second row that this happens. Any ideas?

Here's basically what I have gong on:

results.full_data = {};
obsv = 1;
for 20:1:400
... fill struct met that will hold the data going into results.full_data ...
[results] = buildOutput(counter, met, results);
obsv = obsv+1;
end 
function[results] = buildOutput(obsv, met, results)
z = length(results.full_data)+1;
results.full_data(z,:) = {met.counter(obsv) met.current_date(obsv) met.current_time(obsv) met.action(obsv) met.position(obsv) met.pa(obsv) met.bp(obsv) met.num_shares(obsv) met.entry_price(obsv) met.price(obsv) met.sma(obsv) met.stdev(obsv) met.t_band(obsv) met.tm_band(obsv) met.l_band(obsv) met.lm_band(obsv) met.profit(obsv)};
end

Any advice you'd be able to give would be greatly appreciated

Thank you

Answer 1

The call to length returns the largest dimension, which in your case is 17. So the first time, you write 1 row, then you write the 18th row. Thus leaving 16 empty rows between.

Instead of length use size(results.full_data,1) to return the number of rows.

Note that you could have dispensed with the 'z' calculation altogether and done this:

results.full_data(end+1,:) = { etc etc etc };