# Re: [ferret_users] composite of active phase

```Hi Jaya,
```
Yes, this method looks fine. The sampling that SAMPLEL does is based on index values that refer to L=1,2,3,.... so if you have listed the index values that correspond to the times you want to include, then averaging the sampled variable is the average over just those times.
```
```
To make a list of values before and after the chosen time points, I have an idea. I will show an example to make a list of the index values 5 points before and after a particular list of index values,and you can do the same thing with a list of 20 points before and after. We will define a t variable from the list of indices, and an x variable centered on zero, with 5 points on each side. Then we'll use these variables to define a 2D variable whose values in the x direction will be the set of chosen index values, plus or minus 5. Then we will create a 1D list of this new variable.
```
! A set of points which correspond toyour active phase dates, on a T axis
```
yes? LET tpts = TSEQUENCE({100,150,300})
```! An axis in another direction, centered on zero
yes? DEFINE AXIS/X=-5:5:1 x5
yes? let xpts = x[gx=x5]

yes? LET xtvar = xpts + tpts

yes? list xtvar
VARIABLE : X[GX=X5] + TPTS
SUBSET   : 11 by 3 points (X-T)
```
-5 -4 -3 -2 -1 0 1 2 3 4 5 1 2 3 4 5 6 7 8 9 10 11 1 / 1: 95.0 96.0 97.0 98.0 99.0 100.0 101.0 102.0 103.0 104.0 105.0 2 / 2: 145.0 146.0 147.0 148.0 149.0 150.0 151.0 152.0 153.0 154.0 155.0 3 / 3: 295.0 296.0 297.0 298.0 299.0 300.0 301.0 302.0 303.0 304.0 305.0
```                                               ^
^
```
|---- 5 on each side ------ the original points ------ 5 on each side ----|
```
yes?  ! now make this into a 1D variable

yes? LET xtseries = XSEQUENCE(xtvar)
yes? list xtseries
VARIABLE : XSEQUENCE (XTVAR)
SUBSET   : 33 points (X)
1    /  1:   95.0
2    /  2:   96.0
3    /  3:   97.0
4    /  4:   98.0
5    /  5:   99.0
6    /  6:  100.0  <--
7    /  7:  101.0
8    /  8:  102.0
9    /  9:  103.0
10   / 10:  104.0
11   / 11:  105.0
12   / 12:  145.0
13   / 13:  146.0
14   / 14:  147.0
15   / 15:  148.0
16   / 16:  149.0
17   / 17:  150.0  <--
18   / 18:  151.0
19   / 19:  152.0
20   / 20:  153.0
21   / 21:  154.0
22   / 22:  155.0
23   / 23:  295.0
24   / 24:  296.0
25   / 25:  297.0
26   / 26:  298.0
27   / 27:  299.0
28   / 28:  300.0  <--
29   / 29:  301.0
30   / 30:  302.0
31   / 31:  303.0
32   / 32:  304.0
33   / 33:  305.0

```
See how the points in this list are the set of L indices originally chosen, plus 5 points on each side of them. You can use this in a call to SAMPLEL.
```
yes? let var5  =SAMPLEL(var,xtseries)

```
If you follow this example, but define the x axis with /X=-20:20:1 I think you will have what you need. The output of the samplel function is on an abstract axis, so the result of the example I just did, var5 would have a T axis with T=1,2,3, ... 33.
```
Ansley

jaya kumar A wrote:
```
```dear ferret users,
```
I want to calculate the composite of active phase which corresponds to different dates in the JJAS ,
```if i pick the dates from the different years I tried like this
let SD_posv=SAMPLEL(PRE_ANOM_NEW[d=1],{171, 204, 195, 2002, 12.....})
con/lev=(0.2,2,0.2)/nolab/nokey SD_posv[l=@ave]

will this method is ok?
if it is wrong any good method to make
```
I also want to make a time series of 20 days before and after active phase so if i define SD_posv as active phase (above)
```
with regards
jaya

--
JAYAKUMAR A
Senior Research Fellow,
Theoretical Studies Division
IITM, Pune-8
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