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Questions tagged [mapply]

R function that applies a function to multiple lists or vector arguments.

R function mapply is a multivariate version of sapply. mapply applies FUN argument to the first elements of each argument, the second elements, the third elements, and so on. Arguments are recycled if necessary.

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Naming / Names of the apply function family in R

I'm currently studying R. In particular I need to remember the functions in the apply-function family (e.g. lapply, sapply, mapply, etc.). I know what each function in the apply-function family does (especially this answer helps a lot), but mixes…
Herickson
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Why does mapply not store ggplot objects in the output

When we use mapply in this scenario it will return the actual numbers that resulted from multiplying x and y: mult.fun <- function(x, y) { x*y } res <- mapply(mult.fun, seq(1,3), seq(1,3)) # gives > 1 4 9 Then we can access the results later on…
CodeNoob
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multiply two lists of irregular length

I have lists like a <- list(list(c(-2,1), 4:5, 2:3), list(c(0,2), c(-1,1))) b <- list(7:9, c(5,-1)) > a [[1]] [[1]][[1]] [1] -2 1 [[1]][[2]] [1] 4 5 [[1]][[3]] [1] 2 3 [[2]] [[2]][[1]] [1] 0 2 [[2]][[2]] [1] -1 1 > b [[1]] [1] 7 8…
Christoph Hanck
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Multiple list nesting with split(), R

Given a dataset with multiple unique elements in a column, I'd like to split those unique elements into new dataframes, but have the dataframe nested one level down. Essentially adding an extra level to the split() command. For instance (using…
moxed
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Rename Columns of dataframe based on names of list in R

I have multiple dataframes saved in a list object. They share the same two column names. I'd like to rename the second column to the name of the dataframe. Example Data: df1 <- data.frame(A = 1:10, B= 11:20) df2 <- data.frame(A = 21:30, B = 31:40)…
user6883405
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R: merge two lists of lists of dataframes

I have two lists of lists of dataframes like this: L1 <- list(Q1=list(A=data.frame(X1=1:3),C=data.frame(X1=1:3)), Q2=list(B=data.frame(X1=1:3),C=data.frame(X1=1:3))) L2 <- list(Q1=list(B=data.frame(X1=4:6),C=data.frame(X1=4:6)), …
rosapluesch
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Progress bar and mapply (input as list)

I would like to monitor the progress of my mapply function. The data consists of 2 lists and there is a function with 2 arguments. If I do something similar with a function that takes 1 arguments I can use ldply instead of lapply. (I'd like to…
Roccer
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Struggling with Mapply

So I understand that mapply will step through an array (or series of arrays) in element order – I was wondering if there was a way to STOP it from doing this on some of the arguments…. Let me explain further I have a set of data points, with X and Y…
Karim Awenat
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How to replicate an Exact Binomial Test in R so that it runs through entire columns in a dataframe and generates an output

binom.test(4175, 6534, p = 0.5, + alternative = c("two.sided"), + conf.level = 0.95) Exact binomial test #Output data: 4175 and 6534 number of successes = 4175, number of trials = 6534, p-value < 2.2e-16 …
Alus
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Error when using dplyr::mutate with mapply

I want to use mutate on each of two data frames in a list, adding a column z = 3 to the first and z = 4 to the second (and returning a list of two data frames). dfs <- list(data.frame(x = 1), data.frame(y = 2)) mapply(dplyr::mutate, dfs, z = 3:4,…
Rory Nolan
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extract elements from a list based on a vector of indices

I want to extract elements from a list based on indices stored in a separate vector. This is my attempt at it: list_positions<-c(2,3,4) my_list<-list(c(1,3,4),c(2,3,4,5,6),c(1,2,3,4,6)) my_fun<-function(x,y){ …
Vitalijs
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preserve name of list element when saving using mapply

I'm using mapply() to save elements from a list in separate files. E.g. file.names <- c('~/a.RData', '~/b.RData') data.list <- list(foo = c(1:10), bar = rep(1, 10)) mapply(function(x, y) save(x, file = y), data.list, file.names) and I'd like to…
Lukas
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R: merging lists of data frames on multiple keys

I'm trying to simultaneously merge several data frames in r by combining them into lists and using mapply and merge. This works fine when merging on a single key, but not when merging on multiple keys using the 'by = c("a","b")' argument in merge.…
John Clegg
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Apply multiple functions to two dataframes column-wise

Given the following sample data: library(Metrics) obs=data.frame(replicate(10,runif(100))) pred=data.frame(replicate(10,runif(100))) obs1=as.data.frame(lapply(obs, function(cc) cc[ sample(c(TRUE, NA), prob = c(0.85, 0.15), size = length(cc),…
code123
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Shifting rows of matrices depending on some other data

I'm sorry for repeating a question about the *apply functions, but I cannot get my code to work with the material that I found so far. I have a matrix (stored in a large data frame) and I want to shift the rows of this matrix by a certain amount (to…
Christoph Wockel
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