RBasic3.Rmd

---
title: "R Basic 3"
author: "Raghu Sidharthan"
output: html_document
---
**This page is work in progress**

This is a compilation of basic R utilities. Commonly used items.

[RBasic1](RBasic1),
[RBasic2](RBasic2),
[RBasic3](RBasic3),
[data.table](RDTable),
[dplyr](dplyr),
[tidyr](tidyr),
[RGIS](RGIS),
[Leaflet](Leaflet)

```{r,results='hold'}
#Categorizing each element of a vector into bins based on cutoff points
tstData <- c(4,3,6.9,7,7.1,9)
brks <- c(4,7,8)
(tstData)
(findInterval(tstData, brks))
(findInterval(tstData, brks,all.inside = T))
```

```{r,results='hold',eval=F}
#Replacing the suffix of a column name with another suffix in a data frame
colnames(dset) <- gsub("_insfx","_outsfx",colnames(dset))
#Here all the columns names ending in _insfx will be replaced with _outsfx


#Selecting variables in a dataset that start with a certain prefix
varlist <- c(grep("sampn",colnames(hhga)),grep("numnschd",colnames(hhga)))
hhgaSml <- subset(hhga,select=varlistNeeded)

#Search for  a pattern in a string and get the position number
check <- as.integer(regexpr ("_",fnlPrfl$variable)) 
#search for the position where the first underscore occurs in the variable fnlPrfl$variable
#Substringing a string to get part of thee string (contd. fro above)
fnlPrfl$trippurpD <- substr(fnlPrfl$variable,1,check-2)
fnlPrfl$mseg      <- substr(fnlPrfl$variable,check-1,check-1)
fnlPrfl$todCat    <- substr(fnlPrfl$variable,check+1,check+2)

#Split a string every time a character is encountered
strsplit(ttFmt,split=":")
# This is useful to get hh,mm,ss from a time string in the time format

#Convert Factor variable to character
charVar <- as.character(facVar)

# Date reading conversion
# convert date info in format 'mm/dd/yyyy'
strDates <- c("01/05/1965", "08/16/1975")
dates <- as.Date(strDates, "%m/%d/%Y")
The default format is yyyy-mm-dd
mydates <- as.Date(c("2007-06-22", "2004-02-13"))

#Day of the Week - DOW 
# The wday component of a POSIXlt object is the numeric weekday (0-6 starting on Sunday).
df = data.frame(date=c("2012-02-01", "2012-02-01", "2012-02-02")) 
df$day <- weekdays(as.Date(df$date))
as.POSIXlt(df$date)$wday

# Cumalative sum, products and extremes
cumsum(x)
cumprod(x)
cummax(x)
cummin(x)

#Linear Regression
fit1 <- lm(DIST ~ TRPDUR_C, data=LTRIPCmplt[LTRIPCmplt$modeCat==1,]);fit1
coefficients(fit1)/sqrt(diag(vcov(fit1)))

# Global vs local variable. If you use <- inside a function then it assigns to local. IF you use <<- then it assigns to global variable


#Get index of a particular set of columns and add some number to it – 
sdta <- trt[,list(HHWORK0,HHWORK1,HHWORK2,HHWORK3PLUS)]
out = unlist(apply(sdta,1,which.max))
sdta.mat = as.matrix(data.frame(sdta))
tplt <- matrix(c(1,0,0,0,0,1,0,0,0,0,1,0,0,0,0,1),nrow=4)
tplt <- tplt[out,]*trt$delta


```

```{r,results='hold',eval=F}
59.	Length of a string – nchar
60.	library(stringr)
a.	str_sub("leftright",1,4)
b.	[1] "left"
c.	str_sub("leftright",-5,-1) # means start from 5th last character and go to the 1st last character
d.	[1] "right"
61.	Selecting all variables starting with pattern
a.	ageVars <- names(forMeta)[regexec("AGE",names(forMeta))!=-1]
62.	Applying max, min function to each element in a vector
a.	sapply(inpShp$POPULATION,max,2)
b.	Will return a vector of same length as the input vector capped below at 2.
63.	Write to a a text file
a.	write("\nNumber of Records Stats",file="StatSummary.csv",append=TRUE)
64.	# returns string w/o leading whitespace
65.	trim.leading <- function (x)  sub("^\\s+", "", x)
66.	# returns string w/o trailing whitespace
67.	trim.trailing <- function (x) sub("\\s+$", "", x)
68.	
69.	# returns string w/o leading or trailing whitespace
70.	trim <- function (x) gsub("^\\s+|\\s+$", "", x)
71.	From http://stackoverflow.com/questions/2261079/how-to-trim-leading-and-trailing-whitespace-in-r

# below getting number of participants in a joint activity from the character string
72. jtr$num_participants <- 1+nchar(jtr$tour_participants) - unlist(lapply(gsub(" ", "", jtr$tour_participants, fixed = TRUE),nchar))
```