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Questions tagged [lapply]

lapply is a function in R that returns a list of the same length as given argument X, each element of which is the result of applying given function to the corresponding element of X

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lapply function /loops on list of lists R

I know this topic appeared on SO a few times, but the examples were often more complicated and I would like to have an answer (or set of possible solutions) to this simple situation. I am still wrapping my head around R and programming in general.…
MIH
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Same function over multiple data frames in R

I am new to R, and this is a very simple question. I've found a lot of similar things to what I want but not exactly it. Basically I have multiple data frames and I simply want to run the same function across all of them. A for-loop could work but…
user3272284
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deparse(substitute(x)) in lapply?

I would like use a function that uses the standard deparse(substitute(x)) trick within lapply. Unfortunately I just get the argument of the loop back. Here's my completely useless reproducible example: # some test data a <- 5 b <- 6 li <-…
Matt Bannert
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Union of intersecting vectors in a list in R

I have a list of vectors as follows. data <- list(v1=c("a", "b", "c"), v2=c("g", "h", "k"), v3=c("c", "d"), v4=c("n", "a"), v5=c("h", "i")) I am trying to achieve the following: Check whether any of the vectors intersect with each…
Crops
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how to determine if a character vector is a valid numeric or integer vector

I am trying to turn a nested list structure into a dataframe. The list looks similar to the following (it is serialized data from parsed JSON read in using the httr package). myList <- list(object1 = list(w=1, x=list(y=0.1, z="cat")), object2 =…
Andrew Barr
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zipping lists in R

As a guideline I prefer apply functions on elements of a list using lapply or *ply (from plyr) rather than explicitly iterating through them. However, this works well when I have to process one list at a time. When the function takes multiple…
gappy
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How can I apply a custom function that adds new columns to a dataframe to a subset of existing columns?

I am working with a large dataset where much of the data was entered twice. This means that many of the variables are represented by pairs of columns: column.1 with the data entered by one person, and column.2 where the same data was entered by a…
sf26749
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Convert several columns from integer to numeric in R data.frame

I would like to convert columns from 2 to 13 (the last one) from integer to numeric. For one column, I use the following code: dades$V3 <- as.numeric(dades$V3) I want to convert columns from 2 to 13 with the same command. I create this…
Enric Agud Pique
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can lapply not modify variables in a higher scope

I often want to do essentially the following: mat <- matrix(0,nrow=10,ncol=1) lapply(1:10, function(i) { mat[i,] <- rnorm(1,mean=i)}) But, I would expect that mat would have 10 random numbers in it, but rather it has 0. (I am not worried about the…
stevejb
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Why do rapply and lapply handle NULL differently?

I'm aware that NULL values in lists can sometimes trip people up. I'm curious why in a specific instance lapply and rapply seem to treat NULL values differently. l <- list(a = 1, c = NULL, d = 3) lapply(l,is.null) $a [1] FALSE $c [1] TRUE $d [1]…
joran
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Is it possible to skip NA values in "+" operator?

I want to calculate an equation in R. I don't want to use the function sum because it's returning 1 value. I want the full vector of values. x = 1:10 y = c(21:29,NA) x+y [1] 22 24 26 28 30 32 34 36 38 NA x = 1:10 y = c(21:30) x+y [1] 22 24 26 28…
M. Beausoleil
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Using lapply to change column names of a list of data frames

I'm trying to use lapply on a list of data frames; but failing at passing the parameters correctly (I think). List of data frames: df1 <- data.frame(A = 1:10, B= 11:20) df2 <- data.frame(A = 21:30, B = 31:40) listDF <- list(df1, df2,df3) …
user3310782
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How to apply mean function over elements of a list in R

I have a list and I want to use lapply() to compute the mean of its elements. For example, for the seventh item of the list I have: >list[[7]] [1] 1 1 1 1 1 1 1 1 1 1 and my output should be: > mean(temp[[7]][1:10]) [1] 1 But when I use lapply()…
hora
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Dataframes in a list; adding a new variable with name of dataframe

I have a list of dataframes which I eventually want to merge while maintaining a record of their original dataframe name or list index. This will allow me to subset etc across all the rows. To accomplish this I would like to add a new variable 'id'…
Look Left
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calculate median from data.table columns in R

I am trying to calculate a median value across a number of columns, however my data is a bit funky. It looks like the following example. library(data.table) dt <- data.table("ID" = c(1,2,3,4),"none" = c(0,5,5,3), "ten" =…
Dan
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