[R] match() question or needle haystack problem for a data.frame

[Knut Krueger]

Hi to all

I would like to reduce the "Mydata" to rows, only if Mydata$Data1 are in 
needles



needles =c(14390, 14391, 14392, 14427, 14428, 14429, 14430, 14431, 
14432, 14433, 14434, 14435, 14436, 14437, 14439, 14440, 14441, 15195, 
15196, 15197, 15198, 15199, 15200, 15201, 15202, 15203, 15204, 15205, 
15206, 15207, 15208, 15209, 17615, 17616, 17617, 17618, 17619, 17620, 
17621, 17622, 17623, 17624, 17625, 17626, 17627, 17628, 17629, 17630, 
17631, 17679, 17680, 17681, 17682, 17683, 17823, 17824, 17825, 17826, 
17827, 17828, 17829, 17830, 17831, 17862, 17863, 17864, 17865, 17866, 
17867, 17868, 17869, 17870, 17871, 17872, 17873, 17874, 17875, 17876, 
17877, 17878, 17879, 17880, 17881, 17882, 17883, 19255, 19256, 19257, 
19258, 21289, 21290, 21291, 21292, 22890, 22891, 22892, 22893, 22894, 
22895, 22896, 22897, 22898, 22899, 22900, 22901, 22902, 40428, 40429, 
40430, 40431, 40432, 40433, 40434, 40435, 40436, 40437)

Haystack =c(14390, 14391, 14392, 14427, 14428, 14429, 14430, 14431, 
14432, 14433, 14434, 14435, 14436, 14437, 14439, 14440, 14441, 15187, 
15188, 15195, 15196, 15197, 15198, 15199, 15200, 15201, 15202, 15203, 
15204, 15205, 15206, 15207, 15208, 15209, 16717, 16718, 17615, 17616, 
17617, 17618, 17619, 17620, 17621, 17622, 17623, 17624, 17625, 17626, 
17627, 17628, 17629, 17630, 17631, 17679, 17680, 17681, 17682, 17683, 
17817, 17818, 17823, 17824, 17825, 17826, 17827, 17828, 17829, 17830, 
17831, 17862, 17863, 17864, 17865, 17866, 17867, 17868, 17869, 17870, 
17871, 17872, 17873, 17874, 17875, 17876, 17877, 17878, 17879, 17880, 
17881, 17882, 17883, 17886, 19255, 19256, 19257, 19258, 21289, 21290, 
21291, 21292, 22890, 22891, 22892, 22893, 22894, 22895, 22896, 22897, 
22898, 22899, 22900, 22901, 22902, 40428, 40429, 40430, 40431, 40432, 
40433, 40434, 40435, 40436, 40437, 40710, 40711, 49127, 49128, 52768)

Mydata =data.frame (DATA1=Haystack, Data2=c(1:length(Haystack)))



match(Mydata$DATA1, needles, nomatch=NA) does find all data which are in 
needle - the others are set to the nomatch value.

But I don not find out how to reduce the data.frame  -  maybe match() is 
not helpful for that.

Kind regards Knut