[R] [FORGED] Re: How create columns for squared values from previous columns?

[Göran Broström]

On 2017-04-29 06:45, Mike C wrote:
> Thanks Rolf. I was just a bit frustrated that R wouldn't generate
> dummy variable names on the fly.
>
> Also, another question, if I want to put column 5 at column 3,
>
> dat[, 3:5] <- dat[, c(5,3,4)]
>
> It does not work, why?

It "works", but you need to shuffle the names in the same way:

names(dat)[3:5] <- names(dat)[c(5,3,4)]

Better(?):

perm <- c(1,2,5,3,4)
dat <- dat[perm]

dat is a list.

Göran

>
> ________________________________ From: Rolf Turner
> <r.turner at auckland.ac.nz> Sent: Friday, April 28, 2017 10:48:42 PM
> To: C W Cc: r-help Subject: Re: [FORGED] Re: [R] How create columns
> for squared values from previous columns?
>
> On 29/04/17 13:21, C W wrote:
>> I came up with this solution,
>>
>>> cbind(dat, dat[, 1:3]^2)
>> X1         X2         X3         X4          X5          X1 X2
>> X3 1  0.72776481 -1.1332612 -1.9857503 0.46189400 -0.09016379
>> 0.529641625 1.28428102 3.9432044 2  0.05126592  0.2858707
>> 0.9075806 1.27582713 -0.49438507 0.002628194 0.08172203 0.8237026 3
>> -0.40430146  0.5457195 -1.1924042 0.15025594  1.99710475
>> 0.163459669 0.29780978 1.4218277 4  1.40746971 -1.2279416
>> 0.3296075 0.84411774 -0.52371619 1.980970990 1.50784058 0.1086411 5
>> -0.53841150  0.4750082 -0.4705148 0.05591914 -0.31503500
>> 0.289886944 0.22563275 0.2213842 6  0.90691210  0.7247171
>> 0.8244184 0.73328097 -1.05284737 0.822489552 0.52521494 0.6796657
>>
>> But, you would NOT ONLY get undesired variable names, BUT ALSO
>> duplicated names. I suppose I can use paste() to solve that?
>>
>> Any better ideas?
>
> Well, if the names bizzo is your only worry, you could hit the
> result with data.frame() *after* cbinding on the squared terms:
>
> dat <- matrix(rnorm(30),ncol=5) dat <- cbind(dat,dat[,1:3]^2) dat <-
> data.frame(dat) names(dat)
>
> And as you indicate, the names of a data frame are easily adjusted.
>
> I wouldn't lose sleep over it.
>
> cheers,
>
> Rolf Turner
>
> P.S. You could also do
>
> names(dat) <- make.unique(names(dat))
>
> to your original idea, to get rid of the lack of uniqueness.  The
> result is probably "undesirable" but.
>
> R. T.
>
> -- Technical Editor ANZJS Department of Statistics University of
> Auckland Phone: +64-9-373-7599 ext. 88276
>
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