# [R] indexing question

Benilton Carvalho bcarvalh at jhsph.edu
Mon Nov 13 21:17:58 CET 2006

```diff(tmp[idx])

cheers,

b

On Nov 13, 2006, at 3:06 PM, Leeds, Mark ((IED)) wrote:

> I have the following set of indices, call it idx, that correspond
> to the
> indices of a vector say temp.
>
>  [1]   31   36   41   61   66   71   91   96  101  121  126  131  151
> 156  161  181  186  191  211  216  221  241  246  251  271  276  281
> 301  306  311  331  336  341  361  366
>  [36]  371  391  396  401  421  426  431  451  456  461  481  486  491
> 511  516  521  541  546  551  571  576  581  601  606  611  631  636
> 641  661  666  671  691  696  701  721
>  [71]  726  731  751  756  761  781  786  791  811  816  821  841  846
> 851  871  876  881  901  906  911  931  936  941  961  966  971  991
> 996 1001 1021 1026 1031 1051 1056 1061
> [106] 1081 1086 1091 1111 1116 1121 1141 1146 1151 1171 1176 1181 1201
> 1206 1211 1231 1236 1241 1261 1266 1271 1291 1296 1301 1321 1326 1331
> 1351 1356 1361 1381 1386 1391 1411 1416
> [141] 1421
>
>
> I want to calculate temp[36] - temp[31] and temp[41] - temp[36]
>
> Similarly, temp[66] - temp[61] and temp[71] - temp[66]
> .
> .
> .
> .
> Similarly temp[1416]-temp[1411]
>           temp[1421] - temp[1416]
>
>
> I'm doing this because the above subractions represent pairs of
> returns
> and the correlations between them wil be calculated eventually.
>
> In other words, eventually I will have
>
> X_36_31  ( i.e : temp[36] - temp[31] )
> X_66-61
> X_96-91
> .
> .
> .
> .
> .
> .
> .
> X_1411-1416
>
> as one vector and
>
> Y_41-36
> Y_71-66
> Y_101-96
> .
> .
> .
> .
> .
> Y_1416_1421
>
> as another vector.
>
> and will calculate the correlation between the two vectors in order to
> get one number.
>
>
> The point is I am  really only using the indices 31, 61, 91 etc as
> anchor's so a regular diff(temp[idx]) won't work because it will diff
> all
> the elements that are next to each other ? This is a weird problem.
> I'm
> still thinking about it. I'm hoping to figure it out before someone
> sends me something but I won't mind so much if I get an external
> solution first. I have no pride.
> --------------------------------------------------------
>
> This is not an offer (or solicitation of an offer) to buy/se...
> {{dropped}}
>
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> and provide commented, minimal, self-contained, reproducible code.

```