MATLAB: Storing vectors from a for loop, into a 2d matrix.

arrayfor loopstoringvectorzero

Greetings all,
Hopefully this is a relatively trivial issue, i have observed this short for loop:
>> for r = 1 : 10 vec = [10:20]+r mat(r,1) = vec end
which creates 10 vectors, e.g:
11 12 13 14 15 16 17 18 19 20 21
and stores them in a matrix like this:
11    12    13    14    15    16    17    18    19    20    21
12    13    14    15    16    17    18    19    20    21    22
13    14    15    16    17    18    19    20    21    22    23 ....etc
When i am trying to utilise this for my own project, i need it to be of the form:
for r = 1 : 5 : 16 vec = [10:20]+r mat(r,:) = vec end
which i thought would give:
11 12 13 14 15 16 17 18 19 20 21
16 17 18 19 20 21 22 23 24 25 26 etc.
But i am getting:
    11    12    13    14    15    16    17    18    19    20    21
     0     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0     0
    16    17    18    19    20    21    22    23    24    25    26
     0     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0     0
     0     0     0     0     0     0     0     0     0     0     0
Where do all these 0's erupt from? i must plot the array without the zero's because my actual data is much larger (approx for k = 1: 500: 1000000) and exponential number of 0's just exceeds matlab capabilities.
anyone know a better way of storing these results in a 2d array? thank you, much obliged.
David

Best Answer

Well when r = 1: you index into
mat(r<:)
But then the next iteration r = 6 and you have:
mat(r,:)
So you need to keep a counter:
cnt = 0;
for r = 1:5:16
  cnt = cnt+1;
  mat(cnt,:) = whatever
end
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