dplyr only returning one row when using summarize

Question

I'm just getting around to giving dplyr's chain operator a try.

Using the simple example:

group_by(mtcars, cyl) %>%
summarise(mean(disp), mean(hp))

I get the result:

  # mean(disp) mean(hp)
  #1   230.7219 146.6875

For some reason dplyr isn't grouping, just summarizing the entire vector. What am I missing?

It's true for all data.frames, not just mtcars – Ben Rollert Nov 26 '14 at 19:16 — Ben Rollert, Nov 26 '14 at 19:16
I'm using version .3.0.2 – Ben Rollert Nov 26 '14 at 19:18 — Ben Rollert, Nov 26 '14 at 19:18

Tyler Rinker · Accepted Answer · 2020-07-08T20:54:07.617

45

Start a fresh session this is what I get:

library(dplyr)

mtcars %>%
    group_by(cyl) %>%
    summarise(mean(disp), mean(hp))

##   cyl mean(disp)  mean(hp)
## 1   4   105.1364  82.63636
## 2   6   183.3143 122.28571
## 3   8   353.1000 209.21429

Edit

Don't load plyr second (after dplyr) or at all. The problem is that it's using plyr::summarise not dplyr::summarise:

mtcars %>%
    group_by(cyl) %>%
    plyr::summarise(mean(disp), mean(hp))

##   mean(disp) mean(hp)
## 1   230.7219 146.6875

Edit 2

You could also just be explicit and say which package to pull sumamrise from as seen below:

mtcars %>%
    group_by(cyl) %>%
    dplyr::summarise(mean(disp), mean(hp))

edited Jul 08 '20 at 20:54

answered Nov 26 '14 at 19:17

Tyler Rinker

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2

correct, I was loading plyr as part of my standard set of libraries. Will accept your answer in 9 mins. – Ben Rollert Nov 26 '14 at 19:20
I need `ldply` from `plyr`, is there similar function to avoid loading `plyr`? – ismailsunni Jan 24 '20 at 07:56
ah, I can detach it after I use the function I need :) – ismailsunni Jan 24 '20 at 07:59
1

I didn't import `plyr`. Somehow it was using `plyr`. So, changing to `dplyr::summarize` worked for me. – damjad Jul 08 '20 at 10:49

dplyr only returning one row when using summarize

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