General
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Get Help ? <Object/Function>
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Find the working directory getwd()
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Setting Working directroy setwd("~/specdata")
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List files in working dir dir()
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Load code file into workspace source("file.R")
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Find the type of an object class(my_vector)
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List objects in workspace ls()
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Change page width options(width = 160)
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Operators
Assignement |
var <- <New value> |
Compare two objects |
identical( obj1, obj2 ) |
Equality |
var1 == var2 |
Special Values
NA |
value is Not Available |
NaN |
Not a Number |
Inf |
Infinity |
T |
True |
F |
False |
Subsetting Vectors
First 10 elements |
x[1:10] |
Vector of all NAs |
x[is.na(x)] |
Vector of real values |
x[!is.na(x)] |
Values greater than 0 |
y[y > 0] |
Combine conditions |
x[!is.na(x) & x > 0] |
3rd, 5th, 7th elements of x |
x[c(3,5,7)] |
All but the 2nd and 10th (neg) |
x[c(-2, -10)] or x[-c(2,10)] |
Access element by label |
vect["bar"] or vect[c("foo", "bar")] |
Index vectors come in four different flavors -- logical vectors, vectors of positive integers, vectors of negative integers, and vectors of character strings
Debugging
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Prints function call stack
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Flags a function for "debug" mofr which allows you to step through execution of a function one line at a time
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Suspends the execution of a function, and outs the function in debug mode. n- next
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Allows you to insert debugging code into a function
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Allows you to modify the error behaviour so that you can browse the function call statck
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Vectors
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Concatinate function patients <- c("Bill","Gina","Kelly","Sean")
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Matrices
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Help on matrix type ? matrix
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Add dimensions to vector to make a matrix dim(my_vector) <- c(4, 5)
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View dimesions of a matrix dim(my_matrix)
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View dimesions of a matrix attributes(my_matrix)
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Create a matrix. ( 4x5 containing 1-> 20) my_matrix2 <- matrix( 1:20,4,5 )
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+ Matrices can only contain a single class of data.
+ The first number is the number of rows and the second is the number of columns.
Data Frames
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Create a data frame from avector and matrix my_data <- data.frame(patients, my_matrix)
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Add columns name to data frame colnames(my_data) <- cnames_vector
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Select rows based on column value frame[ frame$col == "val", ]
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Select columns by position
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Conversion
To number |
as.number(x) |
To boolean (logical) |
as.logical(x) |
To comples number |
as.complex() |
Reading Data
# Create empty data frame
data <- data.frame()
#Readfiles id is vector of integers
for ( i in id ){
infile = sprintf("%s/%03d.csv", directory, i)
data <- rbind(data,read.csv( infile ))
}
head(data)
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IF statement
if(<condition>) {
## do something
} else {
## do something else
}
if(<condition1>) {
## do something
} else if(<condition2>) {
## do something different
} else {
## do something different
}
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For Statement
for(i in 1:10) {
print(i)
}
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While Statemement
count <- 0
while(count < 10) {
print(count)
count <- count + 1
}
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Repeat Statement
x0 <- 1
tol <- 1e-8
repeat {
x1 <- computeEstimate()
if(abs(x1 - x0) < tol) {
break
} else {
x0 <- x1
}
}
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next,return
for(i in 1:100) {
if(i <= 20) {
## Skip the first 20 iterations
next
}
## Do something here
}
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next is used to skip an iteration of a loop
Loop functions
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Loop over a list and evaluate a function on each element |
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Same as lapply but try to simplify the result |
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Apply a function over the margins of an array |
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Multivariate version of lapply |
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Used to evaluate a function ( often an anonymous one ) over the margins of an array. |
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x<- list( a = 1:5, b= rnorm(10))
lapply(x,mean)
An annonymous fn for extracting the 1st col of each matrix
>lapply(x,function(elt) elt[,1])
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