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Questions tagged [dplyr]

Use this tag for questions relating to functions from the dplyr package, such as group_by, summarize, filter, and select.

The dplyr package is the next iteration of the package. It has three main goals:

  1. Identify the most important data manipulation tools needed for data analysis and make them easy to use from R.
  2. Provide fast performance for in-memory data by writing key pieces in C++.
  3. Use the same interface to work with data no matter where it's stored, whether in a data.frame, a data.table or a database.

Repositories

Vignettes

Some vignettes have been moved to other related packages.

Other resources

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24676 questions
130
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6 answers

How to select the rows with maximum values in each group with dplyr?

I would like to select a row with maximum value in each group with dplyr. Firstly I generate some random data to show my question set.seed(1) df <- expand.grid(list(A = 1:5, B = 1:5, C = 1:5)) df$value <- runif(nrow(df)) In plyr, I could use a…
Bangyou
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7 answers

Applying a function to every row of a table using dplyr?

When working with plyr I often found it useful to use adply for scalar functions that I have to apply to each and every row. e.g. data(iris) library(plyr) head( adply(iris, 1, transform , Max.Len= max(Sepal.Length,Petal.Length)) ) …
Stephen Henderson
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7 answers

Replacement for "rename" in dplyr

I like plyr's renaming function rename. I have recently started using dplyr, and was wondering if there is an easy way to rename variables using a function from dplyr, that is as easy to use as to plyr's rename?
vergilcw
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Change value of variable with dplyr

I regularly need to change the values of a variable based on the values on a different variable, like this: mtcars$mpg[mtcars$cyl == 4] <- NA I tried doing this with dplyr but failed miserably: mtcars %>% mutate(mpg = mpg == NA[cyl == 4])…
luciano
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6 answers

Sum across multiple columns with dplyr

My question involves summing up values across multiple columns of a data frame and creating a new column corresponding to this summation using dplyr. The data entries in the columns are binary(0,1). I am thinking of a row-wise analog of the…
amo
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112
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5 answers

Gather multiple sets of columns

I have data from an online survey where respondents go through a loop of questions 1-3 times. The survey software (Qualtrics) records this data in multiple columns—that is, Q3.2 in the survey will have columns Q3.2.1., Q3.2.2., and Q3.2.3.: df <-…
Andrew
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107
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7 answers

filter for complete cases in data.frame using dplyr (case-wise deletion)

Is it possible to filter a data.frame for complete cases using dplyr? complete.cases with a list of all variables works, of course. But that is a) verbose when there are a lot of variables and b) impossible when the variable names are not known…
user2503795
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104
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4 answers

dplyr summarise: Equivalent of ".drop=FALSE" to keep groups with zero length in output

When using summarise with plyr's ddply function, empty categories are dropped by default. You can change this behavior by adding .drop = FALSE. However, this doesn't work when using summarise with dplyr. Is there another way to keep empty categories…
eipi10
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101
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9 answers

R dplyr: Drop multiple columns

I have a dataframe and list of columns in that dataframe that I'd like to drop. Let's use the iris dataset as an example. I'd like to drop Sepal.Length and Sepal.Width and use only the remaining columns. How do I do this using select or select_ from…
Navaneethan Santhanam
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100
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6 answers

Getting the top values by group

Here's a sample data frame: d <- data.frame( x = runif(90), grp = gl(3, 30) ) I want the subset of d containing the rows with the top 5 values of x for each value of grp. Using base-R, my approach would be something like: ordered <-…
Richie Cotton
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98
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5 answers

R Conditional evaluation when using the pipe operator %>%

When using the pipe operator %>% with packages such as dplyr, ggvis, dycharts, etc, how do I do a step conditionally? For example; step_1 %>% step_2 %>% if(condition) step_3 These approaches don't seem to work: step_1 %>% step_2 if(condition) %>%…
rmf
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R spreading multiple columns with tidyr

Take this sample variable df <- data.frame(month=rep(1:3,2), student=rep(c("Amy", "Bob"), each=3), A=c(9, 7, 6, 8, 6, 9), B=c(6, 7, 8, 5, 6, 7)) I can use spread from tidyr to change this to wide…
Ricky
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6 answers

dplyr: "Error in n(): function should not be called directly"

I am attempting to reproduce one of the examples in the dplyr package but am getting this error message. I am expecting to see a new column n produced with the frequency of each combination. What am I missing? I triple checked that the package is…
Michael Bellhouse
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3 answers

dplyr mutate with conditional values

In a large dataframe ("myfile") with four columns I have to add a fifth column with values conditionally based on the first four columns. Prefer answers with dplyr and mutate, mainly because of its speed in large datasets. My dataframe looks like…
rdatasculptor
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4 answers

dplyr on data.table, am I really using data.table?

If I use dplyr syntax on top of a datatable, do I get all the speed benefits of datatable while still using the syntax of dplyr? In other words, do I mis-use the datatable if I query it with dplyr syntax? Or do I need to use pure datatable syntax to…
Polymerase
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