Using gsub on columns in R

问题

I have a data frame (data) in R with thousands of rows and 10 columns. 9 of the columns contain factors with several levels.

Here is a small portion of the data frame.

A gr1

10 303.90

11 304.1

12 303.6

13 303.90 obs

14 303.90k

As an example, one factor has a level that is "303.90" and another level that is "303.90 obs". I want to change the "303.90 obs" to "303.90". I am using the following command to edit the names of the level.

data[] = as.data.frame(lapply(data, function(x) {x = gsub("303.90 obs","303.90", fixed = T, x)}))

But this is not changing the level "303.90 obs" to "303.90". It just stays the same. Still this command works for other strings, eg. "303.9" gets changed to "303.90" when I use:

data[] = as.data.frame(lapply(data, function(x) {x = gsub("303.9 obs","303.90", fixed = T, x)}))

Any suggestions to why this might be ?

回答1:

I'm not that familiar with lapply therefore my solution simply loops over the columns of the dataframe. This works as it should.

col1 <- 1:10
col2 <- 21:30
col3 <- c("503.90", "303.90 obs", "803.90sfsdf sf", "203.90 obs", "303.90", "103.90 obs", "303.90", "403.90 obs", "803.90sfsdf sf", "303.90 obs")
col4 <- c("303.90", "303.90 obs", "303.90", "203.90 obs", "303.90", "107.40fghfg", "303.90", "303.90 obs", "303.90", "303.90 obs")

data <- data.frame(col1, col2, col3, col4)

data$col3 <- as.factor(data$col3)
data$col4 <- as.factor(data$col4)

for(i in 3:4) {
  matchedExpression = regexpr(pattern = "\\d+\\.\\d+", text = data[,i])
  data[,i] = regmatches(x = data[,i], m = matchedExpression)
  data[,i] <- as.factor(data[,i])
}

EDIT

OP changed description. To change all factors to 303.90regex is a better solution. However, more information are necessary from the OP to give a general solution e.g. is it only 303.90 which should be changed?

EDIT2

Updated the script since OP provided more information e.g. columns can have different factors than 303.90.

来源：https://stackoverflow.com/questions/49431216/using-gsub-on-columns-in-r

标签

gsub