r - creating a column with replaced values using mutate and dplyr -

this duplicate somewhere on stackoverflow , followup question dplyr mutate replace dynamic variable name.

now trying use variable name new column.

something like:

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

the code below creates new column called varname want replace column 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 doesn't work. think dots notation in play not quite sure how wrap head around it.

thank you.

rather replace mpg's existing hwy variable did following illustrate same thing , put context:

from previous question:

library(dplyr) library(ggplot2) library(lazyeval)  data(mpg)  # "normal" dplyr <- mpg %>% mutate(hwybin=replace(hwy>25,1,0))   # varying rhs varname <- "hwy" b <- mpg %>% mutate_(hwybin=interp(~replace(varname>25, 1 ,0),                                    varname=as.name(varname)))  identical(a, b) 

for particular question:

# varying both rhs , 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)