R: How to replace NA value in specific condition

Question

everyone. I want to replace the NA value with value which is not NA for the same participants. I tried this, but it return the original df, i don't know what happened.

df = data.frame(block = c('1',NA,NA,'2',NA,NA,'3',NA,NA),
                subject = c('31','31','31','32','32','32','33','33','33'))

df[df$subject == 1 & is.na(df$block)] = df[df$subject == 31 &!is.na(df$block)]

# define a for loop with from 1 to n 
for (i in 1: length(unique(df$subject))){
    subjects

    # replace the block with NA in block that is not NA for the same participant    
    df[df$subject == i & is.na(df$block)] = df[df$subject == i & !is.na(df$block)]  
}

Here is what i want to get. enter image description here

Check `?na.locf` from `zoo` package. – Ronak Shah Sep 24 '18 at 02:51 — Ronak Shah, Sep 24 '18 at 02:51
Your example is not reproducible, `df` throws an error. – Maurits Evers Sep 24 '18 at 02:52 — Maurits Evers, Sep 24 '18 at 02:52
@RonakShah it works, really thank you! – Eacher Sep 25 '18 at 02:10 — Eacher, Sep 25 '18 at 02:10

DTYK · Accepted Answer · 2018-09-25T01:45:37.160

0

Using the dplyr and the zoo library, I replaced the NA values in the block column with the previous non-NA row values:

library(dplyr)
library(zoo)

df2 <- df %>%
    do(na.locf(.))

The end result looks as follow:

df2

  block subject
1     1      31
2     1      31
3     1      31
4     2      32
5     2      32
6     2      32
7     3      33
8     3      33
9     3      33

edited Sep 25 '18 at 01:45

answered Sep 24 '18 at 02:58

DTYK

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sorry, there is a mistake in subject column, and i corrected and updated it. – Eacher Sep 25 '18 at 01:31
@user10378590 I have updated my response. Is this what you wanted? – DTYK Sep 25 '18 at 01:37
I'm afraid not, i also update what i want in question's description. – Eacher Sep 25 '18 at 01:39
@user10378590 Updated my response to what you wanted. Cheers! – DTYK Sep 25 '18 at 01:46
it works! Cheers! – Eacher Sep 25 '18 at 02:10

R: How to replace NA value in specific condition

1 Answers1