[R] how to create a new data given a vector of variable names

R. Michael Weylandt michael.weylandt at gmail.com
Tue May 15 07:20:33 CEST 2012 

I think you're making this too hard:

x[, vars]

should do it.

For a smaller example, consider

x <- data.frame(a = 1:5, b = rnorm(5), c = letters[1:5])

x[, c("b","a")]

Best,
Michael

On Tue, May 15, 2012 at 1:12 AM, christy <saunders.christy at ymail.com> wrote:
> hi, please help me on this. I'm very new to R.  I've been figuring out how to
> do this the whole day, and I could not get the correct R code.
>
> Suppose I have a dataframe called x and it consists of 10variables.
>
>>x
>
>          h 1        h 2        h 3         h 4        h 5        h 6
> h 7        h 8        h 9
> 1  0.38971928 0.62884802 0.32708216 0.093909834 0.57773251 0.41258918
> 0.37360577 0.65259411 0.88204799
> 2  0.51890830 0.15949863 0.75715149 0.871781822 0.06321826 0.91844114
> 0.05692871 0.84588084 0.77173376
> 3  0.94057256 0.16100731 0.80961141 0.239716639 0.55804412 0.42854829
> 0.54987115 0.68416629 0.24353692
> 4  0.19895720 0.52955693 0.98471869 0.378197899 0.16774788 0.68029534
> 0.42039730 0.82217244 0.74397124
> 5  0.27899679 0.29145024 0.07198476 0.732466508 0.14887818 0.90658800
> 0.64186885 0.66542828 0.98182923
> 6  0.69375077 0.05840897 0.77325437 0.866099979 0.75063858 0.94230759
> 0.72182389 0.65574673 0.27406027
> 7  0.35033643 0.22525597 0.81657974 0.000762193 0.88383211 0.98120966
> 0.29471244 0.32119662 0.10313222
> 8  0.40616362 0.37962815 0.80085463 0.919385580 0.47183711 0.15078169
> 0.93693666 0.24638847 0.12288727
> 9  0.07939773 0.39030956 0.50235863 0.516507293 0.49247563 0.30633870
> 0.45665595 0.25479969 0.34689089
> 10 0.68677267 0.32089352 0.61330153 0.444584299 0.15588483 0.30584289
> 0.78482250 0.55628942 0.81763581
> 11 0.47406350 0.75586693 0.19546691 0.698137899 0.47609057 0.56439955
> 0.33120842 0.54064656 0.36384570
> 12 0.73796417 0.32741375 0.60800036 0.249716033 0.21919825 0.14749886
> 0.53495852 0.74101013 0.69063797
> 13 0.87890769 0.77631054 0.76307442 0.561350947 0.73865259 0.58031305
> 0.06972116 0.53286669 0.09135791
> 14 0.91022993 0.52290742 0.21219953 0.209784849 0.90892801 0.03580675
> 0.19870342 0.79300520 0.85703181
> 15 0.11331488 0.67744821 0.96226396 0.350925439 0.32038355 0.39465379
> 0.38653925 0.09538576 0.04436648
> 16 0.71950535 0.77548893 0.60316799 0.123102348 0.10200008 0.05392754
> 0.17026972 0.17092818 0.35550621
> 17 0.29593089 0.75526797 0.52088596 0.629731365 0.13592383 0.20219434
> 0.63906356 0.55297375 0.30580842
> 18 0.02915505 0.56244353 0.62397566 0.770202648 0.07929744 0.08574671
> 0.36506494 0.47563923 0.84796898
> 19 0.27369892 0.95739919 0.63443013 0.810165262 0.10230919 0.52165672
> 0.84467928 0.60684813 0.02245486
> 20 0.31494866 0.26169713 0.84314426 0.239598362 0.59996122 0.46954979
> 0.99728261 0.28905422 0.91817317
>          h 10
> 1  0.552413907
> 2  0.130387427
> 3  0.523121318
> 4  0.610000351
> 5  0.005378552
> 6  0.275925081
> 7  0.939273614
> 8  0.152024143
> 9  0.216325412
> 10 0.577869906
> 11 0.484999656
> 12 0.686217251
> 13 0.920351777
> 14 0.924500707
> 15 0.577019180
> 16 0.824386203
> 17 0.130089829
> 18 0.539668426
> 19 0.776488706
> 20 0.992742685
>
>
> and i have a vector of strings which I called vars.
>
>> vars
> [1] "h 8"  "h 4"   "h 10" "h 1"
>
>
> the variables inside vars are subset of the column names of x.  The order is
> important. In my dataframe, I want to obtain the following:
>
>>newdata
>           h 8        h 4        h 10         h 1
>  [1,] 0.65259411 0.093909834 0.552413907 0.38971928
>  [2,] 0.84588084 0.871781822 0.130387427 0.51890830
>  [3,] 0.68416629 0.239716639 0.523121318 0.94057256
>  [4,] 0.82217244 0.378197899 0.610000351 0.19895720
>  [5,] 0.66542828 0.732466508 0.005378552 0.27899679
>  [6,] 0.65574673 0.866099979 0.275925081 0.69375077
>  [7,] 0.32119662 0.000762193 0.939273614 0.35033643
>  [8,] 0.24638847 0.919385580 0.152024143 0.40616362
>  [9,] 0.25479969 0.516507293 0.216325412 0.07939773
> [10,] 0.55628942 0.444584299 0.577869906 0.68677267
> [11,] 0.54064656 0.698137899 0.484999656 0.47406350
> [12,] 0.74101013 0.249716033 0.686217251 0.73796417
> [13,] 0.53286669 0.561350947 0.920351777 0.87890769
> [14,] 0.79300520 0.209784849 0.924500707 0.91022993
> [15,] 0.09538576 0.350925439 0.577019180 0.11331488
> [16,] 0.17092818 0.123102348 0.824386203 0.71950535
> [17,] 0.55297375 0.629731365 0.130089829 0.29593089
> [18,] 0.47563923 0.770202648 0.539668426 0.02915505
> [19,] 0.60684813 0.810165262 0.776488706 0.27369892
> [20,] 0.28905422 0.239598362 0.992742685 0.31494866
>
> I tried to do the following but it does not give me what I want:
>
> x[names(x)==names(x[names(x)%in%vars])]
>
>
> Thank you very much.
>
> ~Christy
>
>
>
>
> --
> View this message in context: http://r.789695.n4.nabble.com/how-to-create-a-new-data-given-a-vector-of-variable-names-tp4630024.html
> Sent from the R help mailing list archive at Nabble.com.
>
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