how to select particular rows of a column vector repeatedly?

I have a column vector containing 360 rows(monthly data, 12*10 years=360) and one column. i want to select monthly data of march, april and may of every year. i.e., I need to select 3rd,4th,5th rows for every 12 rows.like that for the 10 years.

[ANUSHA SOMISETTY]

sorry 30 years data, 12*30=360

Answer 1

[madhan ravi]

I’m not exactly sure what you mean, perhaps:

vector(repmat([3,4,5],1,10))

edit:

vector(sort([3:12:360,4:12:360,5:12:360]))

[ANUSHA SOMISETTY]

thank you. i want to select the march, april and may data for the 30 years. 30 years monthly flow data is in a single column with (30years*12months=360) 360 rows.

data is like

1.3 for jan/2001

4.6 for feb/2001

4 for march/2001

.

.

3.2 for jan 2002

.

.

.

5.6 for december/2030

so 0ut of 360 rows, i need to select 3rd(march2001),4th(april2001),5th(may2001),15th(march2002), 16th, 17th, 27th 28th, 29th,39th,40th,41st....351st, 352nd,353rd (may2030)rows

[madhan ravi]

The edit should be giving what you want.

Answer 2

[Walter Roberson]

mask = ismember(mod( (1:12*10) - 1, 12) + 1, [3 4 5]);
YourVector(mask)

The form mod(x-1,N)+1 is a common formula to transform mod(x, N) which woud return 0 1 2 3 ... N-1, into a function that returns 1 2 3 ... N