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

Bert Gunter bgunter.4567 at gmail.com
Sat Apr 29 16:40:20 CEST 2017

```Also:

"I was just a bit frustrated that R wouldn't generate dummy variable
names on the fly."

That is false. See ?lm  and ?model.matrix

-- Bert
Bert Gunter

"The trouble with having an open mind is that people keep coming along
and sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )

On Sat, Apr 29, 2017 at 1:06 AM, Göran Broström <goran.brostrom at umu.se> wrote:
>
>
> 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
>>
>> [[alternative HTML version deleted]]
>>
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>>
>
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