vault backup: 2023-09-12 21:36:16

Affected files:
content/notes/university/year3/cs3002/cs3002-lab1.md

content/notes/university/year3/cs3002/cs3002-lab1.md

@@ -11,7 +11,8 @@ year: '3'
 ---
 The lab sheet can be found [here](assets/university/year3/R_IntroLab_v3.pdf).
 
-## Notes
+# Notes
+---
 - R is **case-sensitive**, so `view` doesn't work but `View` does.
 - To create scatterplots:
     - Column name:
@@ -35,14 +36,71 @@ The lab sheet can be found [here](assets/university/year3/R_IntroLab_v3.pdf).
     lmfire=line(mydata$ISI~mydata$temp)
     abline(coef(lmfire))
     ```
-
 
-## R Cheatsheets
+## A (very) short introduction to R
+---
+R is for statistical computing and graphics, and iti s a public domain (GNU) project.
+
+To set the working directory: `setwd("/Users/pietra/etc")`.
+
+To check the installed packages: `library()` in the console.
+- To install: `install.packages("geometry")`.
+- We then load: `library("geometry")`.
+
+To remove all variables from memory: `rm(list=ls())`.
+
+To define a vector we use **c** meaning **concatenate**: `b=c(3,4,5)`.
+
+- `rnorm()`: creates random samples from a normal distribution.
+    - `rnorm(10, mean=1.2, sd=3.4)`.
+
+We can then do something like:
+
+```r
+x = rnorm(100)
+plot(x)
+```
+
+In doubt, we can do `help(rnorm)` or even `example(rnorm)`.
+
+- `CTRL+SHIFT+S` runs the whole script, whereas `CTRL+ENTER` runs a line.
+
+### Vectors
+**WE INDEX FROM 1, NOT 0!!!**
+
+- To construct: `vec1 = c(1,4,5,8,10)`.
+    - Alternatively: `vec1 = seq(from=0, to=1, by=0.25)`.
+- To change a value: `vec1[3] = 12`.
+- We can then do things like: `sum(vec1)`.
+
+### Matrices
+2-d vectors.
+
+- To construct: `mat=matrix(data=c(9,2,3,4,5,6),ncol=3)`.
+    - Can also specify `nrow`.
+    - We get:
+
+|        | \[,1\] | \[,2\] | \[,3\] |
+| ------ | ------ | ------ | ------ |
+| \[1,\] | 9      | 3      | 5      |
+| \[2,\] | 2      | 4      | 6      | 
+
+Some operations are: 
+- Address an element: `mat[1,2]`.
+- Select a whole row: `mat[2,]`.
+- Function example: `mean(mat)`.
+
+# R Cheatsheets
 - [Graph Parameters CheatSheet](assets/university/year3/R_Graph_Parameters_CheatSheet.pdf).
 - [Base R CheatSheet](assets/university/year3/Base_R_CheatSheet.pdf).
 - [Data Transformation CheatSheet](assets/university/year3/R_Data_Transformation_CheatSheet.pdf).
 
-## Commands
+- Full manual [here](http://cran.r-project.org/doc/manuals/%20R-intro.pdf).
+- Short [reference card](http://zoonek2.free.fr/UNIX/48_R/all.html).
+- Examples [here](http://rwiki.sciviews.org/doku.php).
+- Typical [user wiki](http://www.statmethods.net/).
+
+# Commands
 ```r
 mydata = read.csv('/Users/pietra/projects/university/year3/cs3002/lab1/forestfires.csv', sep=',')