Rename columns of a data frame by searching column name

Question

I am writing a wrapper to ggplot to produce multiple graphs based on various datasets. As I am passing the column names to the function, I need to rename the column names so that ggplot can understand the reference.

However, I am struggling with renaming of the columns of a data frame

here's a data frame:

df <- data.frame(col1=1:3,col2=3:5,col3=6:8)

here are my column names for search:

col1_search <- "col1"
col2_search <- "col2"
col3_search <- "col3"

and here are column names to replace:

col1_replace <- "new_col1"
col2_replace <- "new_col2"
col3_replace <- "new_col3"

when I search for column names, R sorts the column indexes and disregards the search location.

for example, when I run the following code, I expected the new headers to be new_col1, new_col2, and new_col3, instead the new column names are: new_col3, new_col2, and new_col1

colnames(df)[names(df) %in% c(col3_search,col2_search,col1_search)] <- c(col3_replace,col2_replace,col1_replace)

Does anyone have a solution where I can search for column names and replace them in that order?

Answer 1

require(plyr)
df <- data.frame(col2=1:3,col1=3:5,col3=6:8)
df <- rename(df, c("col1"="new_col1", "col2"="new_col2", "col3"="new_col3"))
df

And you can be creative in making that second argument to rename so that it is not so manual.

Answer 2

> names(df)[grep("^col", names(df))] <- 
                        paste("new", names(df)[grep("^col", names(df))], sep="_")
> names(df)
[1] "new_col1" "new_col2" "new_col3"

If you want to replace an ordered set of column names with an arbitrary character vector, then this should work:

names(df)[sapply(oldNames, grep, names(df) )] <- newNames

The sapply()-ed grep will give you the proper locations for the 'newNames' vector. I suppose you might want to make sure there are a complete set of matches if you were building this into a function.