data frame manipulation with condition

Fri, Feb 24, 2012 9:58 AM

When a factor is used as a subscript it is treated
as its integer codes so explicit conversion to character
is needed if you want to subscript by names:
  > f <- factor(c("One","Three","Two"), levels=c("One","Two","Three"))
  > x <- c(Two=2, One=1, Three=3)
  > x[f]
    Two Three   One 
      2     3     1 
  > x[as.character(f)]
    One Three   Two 
      1     3     2
For most other functions (e.g., %in%, paste, sprintf("%s"))
you do not need an explicit conversion to character, but '['
requires you to choose.

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

-----Original Message-----
From: Sarah Goslee [mailto:sarah.goslee at gmail.com]
Sent: Friday, February 24, 2012 9:39 AM
To: William Dunlap
Cc: Arnaud Gaboury; r-help at r-project.org
Subject: Re: [R] data frame manipulation with condition

On Fri, Feb 24, 2012 at 12:23 PM, William Dunlap <wdunlap at tibco.com> wrote:

Use mult[as.character(df$x)] instead of mult[df$x].
They are different when df$x is a factor and the
character version is what you want.

R will coerce a factor to character to perform the comparison; explicitly
calling as.character() is not necessary:

df$x

[1] AA BB CC AA DD DD

df$x == "AA"

[1]  TRUE FALSE FALSE  TRUE FALSE FALSE

See ?factor for details.

Sarah

?> df<- data.frame(x = c("AA","BB","CC","AA","DD","DD"), y = 1:6)
?> mult <- c(AA = 10, BB = 25,DD=15)
?> df$y <- df$y * mult[as.character(df$x)]
?> df
? ? x ?y
?1 AA 10
?2 BB 50
?3 CC NA
?4 AA 40
?5 DD 75
?6 DD 90

This gets the order right. ?The NA for "CC" is because
your vector of multipliers didn't include an entry for
CC. ?You can either add CC=1 to mult or work only on the
subset of the data which has entries in the mult vector.

?> df<- data.frame(x = c("AA","BB","CC","AA","DD","DD"), y = 1:6)
?> mult <- c(AA = 10, BB = 25,DD=15)
?> i <- as.character(df$x) %in% names(mult)
?> df$y[i] <- df$y[i] * mult[as.character(df$x[i])]
?> df
? ? x ?y
?1 AA 10
?2 BB 50
?3 CC ?3
?4 AA 40
?5 DD 75
?6 DD 90

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of Arnaud

Gaboury

Sent: Friday, February 24, 2012 8:37 AM
To: Uwe Ligges
Cc: r-help at r-project.org
Subject: Re: [R] data frame manipulation with condition

df<- data.frame(x = c("AA","BB","CC","AA","DD","DD"), y = 1:6)
mult <- c(AA = 10, BB = 25,DD=15)
df$y <- df$y * mult[df$x]
df

? ?x ?y
1 AA 10
2 BB 50
3 CC 45
4 AA 40
5 DD NA
6 DD NA

My df is in fact much more longer than the chosen example shown here. It seems your tip didn't do

the

job.
I am expecting this as result :

df

? ?x ?y
1 AA 10 ?----> if df$x==AA, df$y<-1*10
2 BB 50 ? ----> if df$x==BB, df$y<-2*25
3 CC 3 ? ? ? ? NOTHING
4 AA 40 ? ?----> if df$x==AA, df$y<-4*10
5 DD 75 ? ----> if df$x==DD, df$y<-5*15
6 DD 90 ? ----> if df$x==DD, df$y<-6*15

Arnaud Gaboury

A2CT2 Ltd.

-----Original Message-----
From: Uwe Ligges [mailto:ligges at statistik.tu-dortmund.de]
Sent: vendredi 24 f?vrier 2012 17:07
To: Arnaud Gaboury
Cc: r-help at r-project.org
Subject: Re: [R] data frame manipulation with condition



On 24.02.2012 16:59, Arnaud Gaboury wrote:

TY Uwe,

So I will have to write a line for each condition? Right?

In fact I was trying to do something with apply in one line, but couldn't achieve any result. In

fact, all my transformation will be multiplying one object by a specific number according to the

value

of df$x.

In that case:

mult <- c(AA = 10, BB = 25)

Then:


df$y <- df$y * mult[df$x]


Uwe Ligges

Arnaud Gaboury

A2CT2 Ltd.


-----Original Message-----
From: Uwe Ligges [mailto:ligges at statistik.tu-dortmund.de]
Sent: vendredi 24 f?vrier 2012 16:33
To: Arnaud Gaboury
Cc: r-help at r-project.org
Subject: Re: [R] data frame manipulation with condition



On 24.02.2012 16:25, Arnaud Gaboury wrote:

Dear list,

n00b question, but still can't find any easy answer.

Here is a df:


Change

df<-data.frame(cbind(x=c("AA","BB","CC","AA"),y=1:4))

to

? ?df<- data.frame(x = c("AA","BB","CC","AA"), y = 1:4)

to make your object a sensible data.frame.

df

? ? ?x y
1 AA 1
2 BB 2
3 CC 3
4 AA 4


I want to modify this df this way :
? ?if df$x=="AA" then df$y=df$y*10

df$y[df$x=="AA"]<- df$y[df$x=="AA"] * 25

...


Uwe Ligges

? ?if df$x=="BB" then df$y=df$y*25

and so on with other conditions.

TY for any help.

Trading

A2CT2 Ltd.

data frame manipulation with condition

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