R: Built-in Function

R Programming Language was built for Statistics and data analysis which means it has many functions available for this purpose. The function which were already defined in the programming framework. R has a set of function which can be used to perform almost every task for the users.

String Function

Function Description
substr(x, start=n1,stop=n2)It is used to extract or replace substrings in a character vector.
grep(pattern, x , ignore.case=FALSE, fixed=FALSE)It is used for searching  for pattern in x.
sub(pattern, replacement, x, ignore.case =FALSE, fixed=FALSE)It is used for finding pattern in x and replaces it with replacement text.
paste(..., sep="")It is used for concatenation of strings after using sep string to separate them.
strsplit(x, split)It is used for splitting the elements of character vector at splitting points. 
tolower(x)It is used to convert strings to lower case.
topper(x)It is used to convert strings to upper case.

Numeric Functions

Functions Description 
abs(x)It is used to return the absolute value of x.
sqrt(x)It returns the square root of the x.
ceiling(x)It returns the smallest integer value which is larger than or equal to x.
floor(x)It returns the largest integer value which is smaller  than or equal to x.
trunc(x)It is used for performing truncate of the value x.
round(x, digits=n)It returns the round value of x.
cos(x), sin(x), tan(x)It is used to return the cos ,sin or tan values of x.
log(x)It gives natural logarithm. 
log10(x)It gives the common logarithm.
exp(x)It returns exponent.

Statistical Probability Functions

Function Description 
dnorm(x, m=0, sd=1, log=False)It is used for finding the height at each point to a given mean and standard deviation of a probability distribution.
pnorm(q, m=0, sd=1, lower.tail=TRUE, log.p=FALSE)It is used to find cumulative normal probability for q
qnorm(p, m=0, sd=1)It is used to find a number whose cumulative value is same as the probability value.
rnorm(n, m=0, sd=1)It is used to generate random numbers with  normal distribution.
dbinom(x, size, prob)It return the probability density distribution at each point.
pbinom(q, size, prob)It return the cumulative value whose probability value is same.
rbinom(n, size, prob)It return numbers of random values of a given probability from a given sample.
dpois(x, lamba)It is  used to find the probability of x successes in a period when the expected number of events is lambda.
ppois(q, lamba)It is used to find cumulative probability of less than or equal to q successes.
rpois(n, lamba)It return random numbers from the poisson distribution.
dunif(x, min=0, max=1)It provide information about the uniform distribution on the interval from min to max. It gives the density.
punif(q, min=0, max=1)It return the distributed function
qunif(p, min=0, max=1)It return the quantile function
runif(x, min=0, max=1)It generates random deviates

Other Statistical Function

Function Description 
mean(x, trim=0, na.rm=FALSE)It return the mean for x.
sd(x)It return the standard deviation of the object.
median(x)It return the median for x
quantilie(x, probs)It return quantile where x is the numeric vector whose quantile are desired and prob is a numeric vector with probabilities in [0,1]
range(x)It return range.
sum(x)It return sum.
diff(x, lag=1)It return lagged differences, with lag indicating which lag to use.
min(x)It return minimum value.
max(x)It return maximum value.
scale(x, center=TRUE, scale=TRUE)It is used to standardize a matrix.