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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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r mapply vs "bad lapply"

I think I've missed something simple here: I have a list of data.frames, and a list of row numbers to select. Something like this: a <- data.frame(q = c(1,0,0,0), w = c(1,1,0,0), e = c(1,1,1,0), r =…
Giovanni Iacopetti
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Efficient way to find manager's manager's id

I have a database of employees, with their manager's id, in long format (one row per employee per month). I would like to add a column that contains their manager's manager's id (or the id of their skip level manager). Here is a toy dataset: id <-…
BLT
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remove multiple patterns from text vector r

I want to remove multiple patterns from multiple character vectors. Currently I am going: a.vector <- gsub("@\\w+", "", a.vector) a.vector <- gsub("http\\w+", "", a.vector) a.vector <- gsub("[[:punct:]], "", a.vector) etc etc. This is painful. I…
vagabond
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Pasting elements of two vectors alphabetically

Say I have two vectors: a <- c("george", "harry", "harry", "chris", "steve", "steve", "steve", "harry") b <- c("harry", "steve", "chris", "harry", "harry", "george", "chris", "george") What I want to do is paste together the 1st pair, 2nd pair,…
jalapic
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R use mapply on nested list

Using base R, I'd like to use the mapply function on a nested list. For example, in the code below, I'm trying to remove the letter "a" from each element of a nested list. I'd like to replace the last two lines with just a single line of…
user1491868
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R: Using mapply with additional lists as arguments

I have the following list and vectors of parameters: myList <- list(c(3, 0, 1), c(2, 2, 2)) vPar1 <- c(1, 5, 100) vPar2 <- c(100, 5, 1) and I'm trying to draw samples from 3 Beta distributions with shape parameters shape1 = vPar1 and shape2 = vPar2…
Constantinos
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How to do faster list-column operations inside data.table

Due to memory (and speed) issues, I was hoping to do some computations inside a data.table instead of doing them outside it. The following code has 100.000 rows, but I'm working with 40 million rows. library(tictoc) library(data.table) # version…
Telaroz
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r how to use mapply with a data table

I want to do what seems a straightforward application of mapply in a data table. I want to multiply a series of data table columns by the value in another column. Here's my function. y is the single column to multiply the values in the other columns…
JerryN
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Ways to improve for loop for matrix manipulations depending on another matrix

I know improving for loop has been asked tons of times before. We can apply family functions to improve the for loop in R. However is there a way to improve manipulations of a matrix where those manipulations depend on another matrix? What I mean…
rmania
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Return multiple lists in mapply

I have a function which I am applying across a list of data frames or matrices (df) using mapply. The function outputs four different types of data frames (ex. a:d) based on some criteria of transformation of the original data frame, but I am…
Chelsea
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Memory efficiency of rolling max / mins with variable windows in R

I've been working on an exercise where I'm needing to calculate max / mins with a variable window length on some large datasets (~100 - 250 million rows). In short, I have a table showing the start and end index (denoted by "Lookup_table" below)…
Phil
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Use ´mapply´ to create an output

I want to create an output with a bullet point for each entry Data I have one (and only one) row from my data frame: structure(list(Dimensions = 2L, Continuity = structure(2L, .Label = c("", "continuous"), class = "factor"), Differentiability =…
Jan
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Pass function name as argument in mapply?

I would like to pass a function name as an argument in mapply: f2 <- function(a, b) a + b^2 f <- function(a, b, func) func(a, b) f(1, 3, f2) ## returns 10 mapply(f2, 1:2, 3) ## returns [1] 10 11 mapply(function(a, b) f(a, b, f2), 1:2, 3) ##…
Robert McDonald
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mutate() a list based upon another list

In this example, I have two lists tiers <- list("tier 1", "tier 2", "tier 3") main <- list(data.frame(a = c("this", "that")), data.frame(a = c("the other", "that too")), data.frame(a = c("once more", "kilgore…
Steven
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Using mapply for indirect addressing in a data frame

With the following two data frames > d1 keystr keynum 1 abc 5 2 def 2 3 def 7 4 abc 3 > d2 HD 2 3 5 7 1 abc H I J K 2 def L M N P I would like to insert a column d1$val that uses the string in…
Vrokipal
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