How to replace values in dataframe columns based on certain conditions

Question

I have the following dataframe u

   u<- data.frame(a=c("x1","x2","x3","x4","x5","x6","x7"),b=c(2005,2006,2007,2008,2009,2010,2011),c1=c(0.5,0.5,0.5,0.6,0.7,0.9,0.5),c2=c(0.5,0.5,0.5,0.6,0.7,0.9,0.5),c3=c(0.5,0.5,0.5,0.6,0.7,0.9,0.5))
a   b       c1  c2  c3
x1  2005    0.5 0.5 0.5
x2  2006    0.5 0.5 0.5
x3  2007    0.5 0.5 0.5
x4  2008    0.6 0.6 0.6
x5  2009    0.7 0.7 0.7
x6  2010    0.9 0.9 0.9
x7  2011    0.5 0.5 0.5

I want to replace values in column (c1,c2,c3) based on values in column b. So if the value in column b is less than 2008, replace values in column (c1,c2,c3) to 1,2 and 3. The resulting data frame is

 a  b     c1    c2  c3
x1  2005    1   2   3
x2  2006    1   2   3
x3  2007    1   2   3
x4  2008    0.6 0.6 0.6
x5  2009    0.7 0.7 0.7
x6  2010    0.9 0.9 0.9
x7  2011    0.5 0.5 0.5

Try u[which(u$b<2008),3:5] <- rep(1:3,each=3)

count
– count

2016-11-29 15:03:09 +00:00
Commented Nov 29, 2016 at 15:03 — count
– count, Commented Nov 29, 2016 at 15:03

gfgm · Accepted Answer · 2016-11-29 15:08:02Z

1

Without using libraries, or in case you need to generalize this to many c columns, you can do:

u <- data.frame(a=c("x1","x2","x3","x4","x5","x6","x7"),
b=c(2005,2006,2007,2008,2009,2010,2011),
c1=c(0.5,0.5,0.5,0.6,0.7,0.9,0.5),
c2=c(0.5,0.5,0.5,0.6,0.7,0.9,0.5),
c3=c(0.5,0.5,0.5,0.6,0.7,0.9,0.5))

Then use normal brackets notation to subset, and assign the three columns at once:

u[u$b<2008,3:5] <- data.frame(1,2,3)
u
   a    b  c1  c2  c3
1 x1 2005 1.0 2.0 3.0
2 x2 2006 1.0 2.0 3.0
3 x3 2007 1.0 2.0 3.0
4 x4 2008 0.6 0.6 0.6
5 x5 2009 0.7 0.7 0.7
6 x6 2010 0.9 0.9 0.9
7 x7 2011 0.5 0.5 0.5

answered Nov 29, 2016 at 15:08

gfgm

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Comments

Jim Raynor · Accepted Answer · 2016-11-29 14:56:06Z

0

Try this

library(magrittr)

u$c1 %<>% ifelse(u$b < 2008, 1, .)

u$c2 %<>% ifelse(u$b < 2008, 2, .)

u$c3 %<>% ifelse(u$b < 2008, 3, .)

answered Nov 29, 2016 at 14:56

Jim Raynor

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Comments

MikeW · Accepted Answer · 2016-11-29 15:04:54Z

0

I happen to find this to be more intuitive but just a preference.

u$c1[u$b < 2008] <- 1 u$c2[u$b < 2008] <- 2 u$c3[u$b < 2008] <- 3

answered Nov 29, 2016 at 15:04

MikeW

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Comments

Jacob · Accepted Answer · 2016-11-29 15:10:37Z

0

and another way...

library(dplyr)
u %>%
  mutate(c1 = ifelse(b < 2008, 1, c1),
         c2 = ifelse(b < 2008, 2, c2),
         c3 = ifelse(b < 2008, 3, c3)
        )

answered Nov 29, 2016 at 15:10

Jacob

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