R help - Oct 2015 - Change values of a column based on the values of a third

Hello all, 

 

I have a rather easy question. I want to add a column to the database which
will change the values of vector a based on the values to vector b. Any
ideas how?

 

For example:

 

Dat <- data.frame(a=
c('A','A','C','B','D','D','B'),

                                  b=
c('N','N','Y','N','Y','N','N')
)

 

I want to add a column c which will change 'C' to 'D' if column
b is 'Y'.

 

> Dat
  a b c

1 A N A

2 A N A

3 C Y D

4 B N B

5 C Y D

6 C N C

7 B N B

	


Any ideas?

 

Best, 

ioanna

 


	[[alternative HTML version deleted]]

?ifelse

I changed Dat to a. have character type instead of factor, and b.
actually match what you show in your example instead of already having
D.

Dat <- data.frame(a=
c('A','A','C','B','C','C','B'),
b=
c('N','N','Y','N','Y','N','N'),
stringsAsFactors=FALSE )

Dat$c <- with(Dat, ifelse(b == "Y" & a == "C",
"D", a))

In general, I'd recommend you read one of the many excellent R
introductory guides out there.

On Mon, Oct 5, 2015 at 12:10 PM, IOANNA IOANNOU <ii54250 at msn.com>
wrote:
> Hello all,
>
>
>
> I have a rather easy question. I want to add a column to the database which
> will change the values of vector a based on the values to vector b. Any
> ideas how?
>
>
>
> For example:
>
>
>
> Dat <- data.frame(a=
c('A','A','C','B','D','D','B'),
>
>                                   b=
c('N','N','Y','N','Y','N','N')
)
>
>
>
> I want to add a column c which will change 'C' to 'D' if
column b is 'Y'.
>
>
>
>
>> Dat
>
>   a b c
>
> 1 A N A
>
> 2 A N A
>
> 3 C Y D
>
> 4 B N B
>
> 5 C Y D
>
> 6 C N C
>
> 7 B N B
>
>
>
>
> Any ideas?
>
>
>
> Best,
>
> ioanna
>
-- 
Sarah Goslee
http://www.functionaldiversity.org

Either

Dat$c <- ifelse( "Y"==Dat$b, rep( "D", nrow(Dat) ), Dat$a
)

Or (more efficiently)

Dat$c <- Dat$a
Dat$c[ "Y"==Dat$b ] <- "D"

Also, beware of creating data frames without using the stringsAsFactors=FALSE
option if you plan to replace levels like this.
---------------------------------------------------------------------------
Jeff Newmiller                        The     .....       .....  Go Live...
DCN:<jdnewmil at dcn.davis.ca.us>        Basics: ##.#.       ##.#.  Live
Go...
                                      Live:   OO#.. Dead: OO#..  Playing
Research Engineer (Solar/Batteries            O.O#.       #.O#.  with
/Software/Embedded Controllers)               .OO#.       .OO#.  rocks...1k
--------------------------------------------------------------------------- 
Sent from my phone. Please excuse my brevity.

On October 5, 2015 9:10:29 AM PDT, IOANNA IOANNOU <ii54250 at msn.com>
wrote:
>Hello all, 
>
> 
>
>I have a rather easy question. I want to add a column to the database
>which
>will change the values of vector a based on the values to vector b. Any
>ideas how?
>
> 
>
>For example:
>
> 
>
>Dat <- data.frame(a=
c('A','A','C','B','D','D','B'),
>
>                                  b=
c('N','N','Y','N','Y','N','N')
)
>
> 
>
>I want to add a column c which will change 'C' to 'D' if
column b is
>'Y'.
>
> 
>
>
>> Dat
>
>  a b c
>
>1 A N A
>
>2 A N A
>
>3 C Y D
>
>4 B N B
>
>5 C Y D
>
>6 C N C
>
>7 B N B
>
>	
>
>
>Any ideas?
>
> 
>
>Best, 
>
>ioanna
>
> 
>
>
>	[[alternative HTML version deleted]]
>
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