## 5.6 Tricks

There are some minor tricks to help you in coding. For long codes, we sometimes want to calculate the time required to complete a task, and we might improve the efficiency of the code if it is too slow.

### 5.6.1 Timing code

To get the current time, we may use Sys.time(). Put this at the beginning and the end of the code. Then the difference is the run time.

t1 <- sys.time()
#…run code here …#
t2 <- sys.time()
t2-t1

### 5.6.2 Suppress annoying message

R tends to give a lot of warning and messages when you run a long code. Sometimes you want to suppress them to keep your console window clean.

suppressMessage(…)
suppressWarnings(…)

### 5.6.3 All files names in a folder

The function list.files will find all files in a folder.

# full.names = TRUE for full path
filenames <- list.files(path = "./folder/", full.names = TRUE)

Using Reduce() and lapply() we can read all csv files from the folder, and merge them together

setwd("C:/path")
file.names <-list.files(path = ".",
pattern="*.csv",
full.names = TRUE)
file.list <- lapply(file.names,
function(x){
file.list)