standard evaluation in dplyr: summarise a variable given as a character string

by

Please note that this answer does not apply to dplyr >= 0.7.0, but to previous versions.

[dplyr 0.7.0] has a new approach to non-standard evaluation (NSE) called tidyeval. It is described in detail in vignette("programming").

The dplyr vignette on non-standard evalutation is helpful here. Check the section “Mixing constants and variables” and you find that the function interp from package lazyeval could be used, and “[u]se as.name if you have a character string that gives a variable name”:

library(lazyeval)
df %>%
  select(-matches(drp)) %>%
  group_by_(key) %>%
  summarise_(sum_val = interp(~sum(var, na.rm = TRUE), var = as.name(val)))
#   v3 sum_val
# 1  A      21
# 2  B      19

More Related Contents:

  1. Why does summarize or mutate not work with group_by when I load `plyr` after `dplyr`?
  2. Summarizing multiple columns with dplyr? [duplicate]
  3. Relative frequencies / proportions with dplyr
  4. Unique rows, considering two columns, in R, without order
  5. Filter data frame by character column name (in dplyr)
  6. How to number/label data-table by group-number from group_by?
  7. Remove duplicated rows using dplyr
  8. dplyr summarise: Equivalent of “.drop=FALSE” to keep groups with zero length in output
  9. dplyr: “Error in n(): function should not be called directly”
  10. dplyr: inner_join with a partial string match
  11. Can dplyr summarise over several variables without listing each one? [duplicate]
  12. R – add column that counts sequentially within groups but repeats for duplicates
  13. Change value of variable with dplyr
  14. Means multiple columns by multiple groups [duplicate]
  15. sample rows of subgroups from dataframe with dplyr
  16. Assigning Dates to Fiscal Year
  17. filter function in dplyr errors: object ‘name’ not found
  18. How to speed up subset by groups
  19. Number of significant digits in dplyr summarise
  20. Create a ranking variable with dplyr?
  21. How to pass dynamic column names in dplyr into custom function?
  22. R – Group by variable and then assign a unique ID [duplicate]
  23. dplyr::mutate to add multiple values
  24. R sum a variable by two groups [duplicate]
  25. Join two data frames in R based on closest timestamp
  26. Conditionally Count in dplyr
  27. data.table row-wise sum, mean, min, max like dplyr?
  28. Update/Replace Values in Dataframe with Tidyverse Join
  29. Collapse all columns by an ID column [duplicate]
  30. dplyr – Group by and select TOP x %

Leave a Comment