user2916044 user2916044 - 3 years ago 136
R Question

R-create a data frame with 2 rows in a loop

How can I create a data frame with 2 rows with this structure?

X1 Y1 Calc1 X2 Y2 Calc2 … Xn Yn Calcn
1 4 0.25 2 5 0.4 i i+3 i/i+3

I tried using this code:

dataRowTemp<-numeric(length = 0)
dataRow<-numeric(length = 0)
headerRowTemp<-character(length = 0)
headerRow<-character(length = 0)

for (i in 1:150){
X<- i
Y<- i+3
Calc <- X/Y
dataRowTemp <- c(X,Y,Calc)
headerRowTemp <- paste(c("X", i),c("Y", i),c("Calc", i),sep='')

unfortunately, I can’t create the a correct header (titleRow) and how can I combine them to data.frame later?

Is there an elegant and better way to do so?

Answer Source

Build a function to be used in each iteration.

myfun <- function(i) {
  X <- i
  Y <- i + 3
  c(X = X, Y = Y, Calc = X/Y)

Set the number of iterations.

n <- 150

Apply the function to the numbers from 1 to n, use matrix(..., nrow = 1) to store the output in a matrix of only 1 row, and transform it into a data.frame (because it is what you say you aim at).

mydf <- data.frame(matrix(sapply(seq_len(n), myfun), nrow = 1))

Use paste0 in a loop to iteratively assign names to the column of your data.frame.

names(mydf) <- c(sapply(seq_len(n), function(i) paste0(c('X', 'Y', 'Calc'), i)))
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