Change-negative-values-in-dataframe-column-to-absolute-value.R

#Change negative values in dataframe column to absolute value
df <- data.frame(c(1:4,NA),c(-1:-3,NA, NA),row.names = LETTERS[1:5])
colnames(df) <- c("positive", "negative")
df

##   positive negative
## A        1       -1
## B        2       -2
## C        3       -3
## D        4       NA
## E       NA       NA

abs(df)

##   positive negative
## A        1        1
## B        2        2
## C        3        3
## D        4       NA
## E       NA       NA

class(df)

## [1] "data.frame"

df[] <- lapply(df, abs)
df

##   positive negative
## A        1        1
## B        2        2
## C        3        3
## D        4       NA
## E       NA       NA

class(df)

## [1] "data.frame"

####################
df[df == "3"] <- "AA"
df

##   positive negative
## A        1        1
## B        2        2
## C       AA       AA
## D        4     <NA>
## E     <NA>     <NA>

#ref https://stackoverflow.com/questions/22306175/change-negative-values-in-dataframe-column-to-absolute-value