creating a column with replaced values using mutate and dplyr

0
votes

This likely a duplicate somewhere on stackoverflow and is a followup question to dplyr mutate replace dynamic variable name.

Now I am trying to use a variable name as the new column.

Something like:

 library(ggplot2)
 data(mpg)
 mpg %>% mutate(hwy=replace(hwy, hwy>29,10))

The code below creates a new column called varname but I want to replace the column with hwy.

varname = "hwy"
mpg %>% mutate_(varname=interp(~replace(varname, varname>29, 10), varname=as.name(varname)))

Something like:

mpg %>% mutate_(as.name(varname)=interp(~replace(varname, varname>29, 10), varname=as.name(varname)))

but this doesn't work. I think the dots notation is in play but not quite sure how to wrap my head around it.

Thank you.

1
rdplyr
I think you want something like this answer – aosmith

1 Answers

1
votes

Rather than replace mpg's existing hwy variable I did the following to illustrate the same thing and put it into context:

From your previous question:

library(dplyr)
library(ggplot2)
library(lazyeval)

data(mpg)

# "normal" dplyr
a <- mpg %>% mutate(hwybin=replace(hwy>25,1,0))


# varying just the RHS
varname <- "hwy"
b <- mpg %>% mutate_(hwybin=interp(~replace(varname>25, 1 ,0),
                                   varname=as.name(varname)))

identical(a, b)

For this particular question:

# varying both RHS and LHS

colname <- "hwybin"
z <- mpg %>% mutate_(.dots=setNames(list(interp(~replace(varname>25, 1 ,0),
                            varname=as.name(varname))), colname))

# tests
identical(a, z)
identical(b, z)