Thomas Manke
Best practice:
Each R project should have their dedicated directory. This directory will hold code, data, results etc.
Task: Open a new project with “File > New Project …”
Notice the following distinction:
Task: Familiarize yourself with the layout and the various panels in Rstudio.
Query: Utilization: https://pollev.com/thomasmanke101
For now, the most important panel is the so-called “Console” with the prompt (“>”).
This is where the first interactions with the R-software will take place.
The other panels are for: output, help and other information.
Task: In the Console try to repeat and understand the following operations
[1] 4[1] 8[1] 3.5[1] 1.414214[1] 1[1] Inf[1] NaNAll R-commands are tracked in a history. It maybe accessed using the cursors (or the history panel in RStudio). This is extremely useful to navigate to previous commands, repeat them, or change them slightly.
Task: Using the history, determine \(\sqrt 3\).
There are various different ways to get help
Use help to find out more about: sqrt, exp or anything else of interest.
Every language operates in a certain context and is context-dependent.
Software depends on other software and packages.
It is important to be aware of those (often complex) dependencies.
One way to communicate this context is with the output from sessionInfo().
R version 4.2.3 (2023-03-15)
Platform: x86_64-conda-linux-gnu (64-bit)
Running under: Ubuntu 22.04.4 LTS
Matrix products: default
BLAS/LAPACK: /home/runner/micromamba/envs/Rintro/lib/libopenblasp-r0.3.27.so
locale:
[1] LC_CTYPE=C.UTF-8 LC_NUMERIC=C LC_TIME=C.UTF-8
[4] LC_COLLATE=C.UTF-8 LC_MONETARY=C.UTF-8 LC_MESSAGES=C.UTF-8
[7] LC_PAPER=C.UTF-8 LC_NAME=C LC_ADDRESS=C
[10] LC_TELEPHONE=C LC_MEASUREMENT=C.UTF-8 LC_IDENTIFICATION=C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] compiler_4.2.3 fastmap_1.1.1 cli_3.6.2 tools_4.2.3
[5] htmltools_0.5.8.1 yaml_2.3.8 rmarkdown_2.25 knitr_1.46
[9] jsonlite_1.8.8 xfun_0.43 digest_0.6.35 rlang_1.1.3
[13] evaluate_0.23 Query: Using sessionInfo() determine which R-version you are running.
Goal: store results of computation in new variables
[1] 6.283185[1] 2[1] FALSE[1] 4Task: look at the following objects and understand the differences
Vectors illustrate how complex data structures can be built from smaller blocks. Here we learn how to create and inspect vectors.
Frequently we need to access specific elements from a vector
Task: access the following vector elements: v[1], v[2], v[3], v[1:3], v[-1]
Tasks:
[1] 2.000 1.025 0.050 -0.925 -1.900Task: Understand the difference between the two vectors v1 and v2
num [1:5] 2 1.025 0.05 -0.925 -1.9[1] "double"[1] "numeric"[1] 5[1] -1.900 -0.925 0.050 1.025 2.000[1] 0.25 Min. 1st Qu. Median Mean 3rd Qu. Max.
-1.900 -0.925 0.050 0.050 1.025 2.000 Task: Define your own vectors and explore some functions and operations (sort, rank, …)
---
title: "01: First Steps"
author: "Thomas Manke"
categories:
- vectors
- indexing
---
# Create R project
**Best practice:**
Each R project should have their dedicated directory. This directory will hold code, data, results etc.
**Task**: Open a new project with "File > New Project ..."
Notice the following distinction:
- When running Rstudio locally, the project directory will reside on your **local** computer.
- When accessing a web server, the project directory will also be on that server.
**Task**: Familiarize yourself with the layout and the various panels in Rstudio.
**Query**: Utilization: https://pollev.com/thomasmanke101
# Console and Commands
For now, the most important panel is the so-called "Console" with the prompt (">").
This is where the first interactions with the R-software will take place.
The other panels are for: output, help and other information.
**Task**: In the Console try to repeat and understand the following operations
```{r console}
2+2
2^3 # This is a comment: try also 2**3
1+2+3/6 # beware of precedence rules
sqrt(2) # functions
sin(pi/2) # functions and built-in constants
# Special values
1/0 # R knows infinity! Try 1/Inf and 1/inf
0/0 # Not a number! Try sqrt(-1)
```
# Command History
All R-commands are tracked in a *history*. It maybe accessed using the cursors (or the history panel in RStudio). This is extremely useful to navigate to previous commands, repeat them, or change them slightly.
**Task**: Using the history, determine $\sqrt 3$.
# First help
There are various different ways to get help
```{r help, eval=FALSE}
?sin
```
Use help to find out more about: sqrt, exp or anything else of interest.
# Community help
* online courses: https://software-carpentry.org/lessons, Coursera, Udacity, ...
* bootcamp: https://github.com/jknowles/r_tutorial_ed
* QuickR: https://www.statmethods.net
* https://stackoverflow.com, https://www.r-bloggers.com/
# SessionInfo
Every language operates in a certain context and is context-dependent.
Software depends on other software and packages.
It is important to be aware of those (often complex) dependencies.
One way to communicate this context is with the output from sessionInfo().
```{r sessionInfo}
sessionInfo()
```
**Query**: Using sessionInfo() determine which R-version you are running.
****
# Assigning values to objects
**Goal**: store results of computation in new variables
```{r simple_obejcts}
x <- 2*pi # pre-defined constant pi
x # see value of object x = show(x)
x = 2 # "=" as in most other languages.
x # x was overwritten
x==3 # another logical comparison (x unchanged)
x+x # passing objects to functions (+)
```
**Task**: look at the following objects and understand the differences
```{r more_obejects, eval=FALSE, echo=TRUE}
pi
hi
"hi"
```
****
# Simple Vectors
Vectors illustrate how complex data structures can be built from smaller blocks.
Here we learn how to create and inspect vectors.
```{r vectors}
v=c(1,2) # combine arguments into vector
v # display v
```
# Accessing Vectors
Frequently we need to access specific elements from a vector
```{r access}
v[1]
```
**Task**: access the following vector elements: v[1], v[2], v[3], v[1:3], v[-1]
# Vector Generation
```{r vector_generation}
v=c(1,2,3,4,5) # combining many elements can get cumbersome
v=1:5 # more efficient
v=seq(from=1, to=5, by=1) # same as before but more flexibilty
v=seq(1,5,0.5) # short-hand defaults
```
**Tasks**:
- Explore the seq() function and inspect other parameter options.
- Create a vector with 5 numbers equally spaced from +2 to -1.9
```{r, echo=FALSE}
v=seq(2,-1.9,length.out=5)
v
```
**Task**: Understand the difference between the two vectors v1 and v2
```{r, eval=FALSE}
v1=1:10-1
v2=1:(10-1)
```
# Functions for vectors
```{r vectors_funcs}
str(v) # structure of v (especially useful for long and structured objects)
typeof(v) # type of v ( ~ storage mode)
class(v) # class of v (determines how certain functions will work with v)
length(v) # length
rev(v) # reverse vectors
sum(v)
summary(v)
```
# Vector Operations
```{r vector_ops, eval=FALSE}
v1=1:3 # = c(1,2,3)
v2=rep(2,3) # = c(2,2,2)
v1 + v2 # elementwise addition
v1 * v2 # ... multiplication
v1 > v2 # ... comparisons
v1 %*% v2 # scalar product
```
**Task**: Define your own vectors and explore some functions and operations (sort, rank, ...)
# Misc: Concepts and Pecularities
```{r misc, eval=FALSE}
v=1:4 # Vector Definition
v + 10 # Recycling
v + c(10,20) # Recycling
v + c(10,20,30) # Warning != Error
#v %*% c(10,20,30) # Error = Error
```
# Naming of Vectors
```{r naming, eval=FALSE}
v=1:4
names(v)
letters # built-in vector. Try LETTERS
typeof(letters) # there is more than numbers
names(v)=letters[1:4] # naming of vector elements (for convenience)
v["b"] # index by name
```
****
# Learning Curve:
* Rstudio: Starting an R project
* work with console
* simple functions (input, output), logical operations and parameters
* creating simple objects and assigning values
* inspecting objects: v, str(v), typeof(v), length(v)
* flexible creation of vectors
* vector indices and subsetting
* vector operations and recycling
* special values: Inf, NaN, NA
* functions can behave differently on different input: summary()
* see warning messages and errors
* getting help: ?sqrt
* software dependencies and the importance of sesssionInfo()