apply

I have a vector of strings. d <- c("Mon","Tues","Wednes","Thurs","Fri","Satur","Sun") for which I want to paste the string "day" on each element of the vector in a way similar to this. week <- apply(d, "day", paste, sep='') No need for apply() , just use paste() : R> d <- c("Mon","Tues","Wednes","Thurs","Fri","Satur","Sun") R> week <- paste(d, "day", sep="") R> week [1] "Monday" "Tuesday" "Wednesday" "Thursday" [4] "Friday" "Saturday" "Sunday" R> Other have already indicated that since paste is vectorised, there is no need to use apply in this case. However, to answer your question: apply is

I want to convert variables into factors using apply() : a <- data.frame(x1 = rnorm(100), x2 = sample(c("a","b"), 100, replace = T), x3 = factor(c(rep("a",50) , rep("b",50)))) a2 <- apply(a, 2,as.factor) apply(a2, 2,class) results in: x1 x2 x3 "character" "character" "character" I don't understand why this results in character vectors instead of factor vectors. Marek apply converts your data.frame to a character matrix. Use lapply : lapply(a, class) # $x1 # [1] "numeric" # $x2 # [1] "factor" # $x3 # [1] "factor" In second command apply converts result to character matrix, using lapply : a2 <-

I have a dataframe and I would like to apply a function that takes the values of three columns and computes the minimum difference between the three values. #dataset df <- data.frame(a= sample(1:100, 10),b = sample(1:100, 10),c= sample(1:100, 10)) #function minimum_distance <- function(a,b,c) { dist1 <- abs(a-b) dist2 <- abs(a-c) dist3 <- abs(b-c) return(min(dist1,dist2,dist3)) } I am looking for something like: df$distance <- sapply(df, function(x) minimum_distance(x$a,x$b,x$c) ) ## errormessage Error in x$a : $ operator is invalid for atomic vectors While I can use ddply: df2 <- ddply(df,.(a

I tried this: // mod.js var a = 1; this.b = 2; exports.c = 3; // test.js var mod = require('./mod.js'); console.log(mod.a); // undefined console.log(mod.b); // 2 console.log(mod.c); // 3, so this === exports? So I image that require() may be implement like this: var require = function (file) { var exports = {}; var run = function (file) { // include "file" here and run }; run.apply(exports, [file]); return exports; } Is that right? Please help me to understand require(), or where can I find the source code. Thanks! Source code is here . exports / require are not keywords, but global variables.

Here's a dataframe: A B C 0 6 2 -5 1 2 5 2 2 10 3 1 3 -5 2 8 4 3 6 2 I could retrieve a column which is basically a tuple of columns from the original df using df.apply : out = df.apply(tuple, 1) print(out) 0 (6, 2, -5) 1 (2, 5, 2) 2 (10, 3, 1) 3 (-5, 2, 8) 4 (3, 6, 2) dtype: object But if I want a list of values instead of a tuple of them, I can't do it, because it doesn't give me what I expect: out = df.apply(list, 1) print(out) A B C 0 6 2 -5 1 2 5 2 2 10 3 1 3 -5 2 8 4 3 6 2 Instead, I need to do: out = pd.Series(df.values.tolist()) print(out) 0 [6, 2, -5] 1 [2, 5, 2] 2 [10, 3, 1] 3 [-5, 2