Florian Richard Florian Richard - 1 year ago 84
R Question

r - How to make this loop faster?

I am reading the

file named
which looks like this:

enter image description here

It goes from
and has 4,166 rows. The following code then creates a new file for each column, compute the approximate entropy using the
function, and prints the value. I know creating a new file for each column is very tedious but I could not find another to do it.

equityreturn <- read.csv("cleanequityreturns.csv", header=T)
for(i in 1:299) {
file2 = paste(i, "equityret.csv", sep="")
file5 = paste("r", i, sep="")
file1 = subset(equityreturn, select=file5)
write.table(file1, file2, sep="\t", row.names=FALSE, col.names=FALSE)
file3 = paste("equity", i, sep="")
file3 = matrix(scan(file = file2), nrow=4166, byrow=TRUE)
print(approx_entropy(file3, edim = 4, r=0.441*sd(file3), elag = 1))

My problem is the following: it takes a long time for the code to perform these tasks. I tried running it for 10 columns and it took about 20 min, which translates in about 10h for all of the 299 columns. Also, this code prints each approximate entropy values, so I still have to copy and paste them in Excel to use them.

How could I make this code run faster and write the output in a

Answer Source

Simply use lapply() as running a dataframe through it processes columns iteratively:

equityreturn <- read.csv("cleanequityreturns.csv", header=T)

entropy_values <- lapply(equityreturn, function(col) {
        approx_entropy(col, edim = 4, r = 0.441*sd(col), elag = 1)
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