R - Lab 1 Flashcards
text
Makes a comment.
Use comments frequently
3+5
Addition
8
2*3
Multiplication
6
4^2
Exponents
16
exp(1.5)
Calculates e to the 1.5 power
x=exp(1.5)
Makes variable ‘x’ equal to exp(1.5)
Doesn’t report anything
Recalling a variable
Type the variable
Ex: If x=exp(1.5)
x
4.481689
log(x)
Natural log of x
What happens if you write incomplete code?
Example:
x=exp(1.5
R will give a ‘+’ on the next line
- Either finish (type ‘)’ ) or press escape
How to scroll through history of commands?
Up and down arrows
How to bring up the help file for a command?
help([command])
So:
help(exp)
How to search for functions that include a certain word?
??’[text]’
??’exponentiate’
What letter must you put in front of parenthesis to create a vector (list of values)?
c
Example vector
x=c(4,5,6)
In vectors:
x[2]
Tells us the 2nd value of x.
If
x=c(4,5,6)
Then
x[2]= 5
What will exp(x) do if x contains a vector?
Calculate exp to the power of each value in x; return a list of scalars.
What is a function?
Any command that takes arguments (in parentheses) and returns results based on a calculation.
Example functions
log(x)
exp(x)
What is a matrix?
A block of numbers with multiple rows and columns.
How to create a matrix in R?
- Create at least two vectors.
Ex:
year=c(1800,1850,1900,1950)
carbon=c(8,54,534,1630) - Assign the data.frame() function to a variable.
Ex:
datum=data.frame(Year=year,Carbon=carbon) - View by typing the variable
Ex:
datum shows the matrix
datum[2] shows just the second column
How do you show the data of just a column AS a column? How do you show the data of a column AS a row of text?
Column
datum[2]
Row of text
datum$Carbon
What are the three easy summaries/analyses of data?
summary(datum)
- provides mean and quartile
head(datum)
[SAYS ‘checks that data was imported properly’ but seems like python head()]
names(datum)
Gives you attributes of data or other objects
How do you make a simple plot?
plot(datum)
X-axis is the first variable in the matrix
plot(Carbon~Year) doesn’t work. Why?
‘Carbon’ and ‘Year’ don’t exist outside the datum data.frame
If you can’t reference the column names outside of the dataframe, how do you plot it?
plot(Carbon~Year,data=datum)
Another way of doing plots
plot(x=datum$Year,y=datum$Carbon)
How do you clear console, and does it eliminate objects you’ve created?
“Edit” option in top left > “Clear Console”
This does NOT eliminate the objects you created.
How do you list all the objects in memory?
ls()
Think “list”
How do you remove objects in memory?
rm()
How do you load a package? What’s a prerequisite?
Pre: Package is installed. Giggidy.
Ex:
library(nlme)
What is the code to load data into R?
datum=read.csv(file.choose())
