How do I create a repeating number series?

Hi guys,

I am doing some work with data taken every 30 minutes over a period of 5 years. For one of the equations I need to use in the programme, it requires a term called 'h', which refers to the midpoint of the calculation period, with units of hours (written as a decimal) of the day. For instance, for the midpoint between 14:00 and 14:30, h=14.25, and for the midpoint of 14:30 and 15:00, h=14.75.

My problem is generating this term h to use in equations.

My total value for the amount of terms in this dataset is a value around 87,000.

So far I have made this:

h=0.25;
n=49;
for i=1:n
    h(i+1)=h(i)+0.5
end

which generates:

  Columns 1 through 11

    0.2500    0.7500    1.2500    1.7500    2.2500    2.7500    3.2500    3.7500    4.2500    4.7500    5.2500

  Columns 12 through 22

    5.7500    6.2500    6.7500    7.2500    7.7500    8.2500    8.7500    9.2500    9.7500   10.2500   10.7500

  Columns 23 through 33

   11.2500   11.7500   12.2500   12.7500   13.2500   13.7500   14.2500   14.7500   15.2500   15.7500   16.2500

  Columns 34 through 44

   16.7500   17.2500   17.7500   18.2500   18.7500   19.2500   19.7500   20.2500   20.7500   21.2500   21.7500

  Columns 45 through 50

   22.2500   22.7500   23.2500   23.7500   24.2500   24.7500

This is what I want, however this only represents one day. I want to make this series repeat so after 24.75 of one day, the sequence resets to 0.25 for the new day and this sequence repeats itself for every day in the dataset, which is all 87,000 data points. How would I do this?

Thanks, Rob

Answer 1

[John D'Errico]

LEARN TO USE MATLAB.

0.25:.5:25
ans =
  Columns 1 through 11
         0.25         0.75         1.25         1.75         2.25         2.75         3.25         3.75         4.25         4.75         5.25
  Columns 12 through 22
         5.75         6.25         6.75         7.25         7.75         8.25         8.75         9.25         9.75        10.25        10.75
  Columns 23 through 33
        11.25        11.75        12.25        12.75        13.25        13.75        14.25        14.75        15.25        15.75        16.25
  Columns 34 through 44
        16.75        17.25        17.75        18.25        18.75        19.25        19.75        20.25        20.75        21.25        21.75
  Columns 45 through 50
        22.25        22.75        23.25        23.75        24.25        24.75

The point is, the colon operator would be nearly the first thing you would learn were you to read the getting started tutorial in MATLAB. Don't skip reading the manual.

Next, you want to repeat this. For how many days? You can count how many you need for 5 years. The simplest way to repeat a vector is to use repmat. So you might end up with this:

h = repmat(0.25:.5:25,1,5*365);

Again, repmat is one of those things you will see in the basic getting started tutorials. READ THEM, as they were put there for you to use and learn from. Otherwise, you will be asking dozens of basic questions you would have learned the answer to in just a few minutes of reading.

[Robert Earles]

Thank you very much.

Yeah I should read the manual. Basically I’m at uni and I was put on a course by them which I’m assuming is different to the manual. I have read about colon operator and I understand how that works as well as some other basic functions, however for some reason I just thought a for loop would be the way to go. But yes using colon operator makes a lot more sense.

With regards to repmat, I didn’t come across that in my course so I will definitely check back to the manual to avoid future simple issues.

Thanks again!