R BASIC | EntropyObserver

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1.R Data Structures Summary Table

Category	Topic / Method	Example Code	Output / Explanation
Objects	Create objects	`x <- 8`	`x` is a numeric object: `8`
ㅤ	ㅤ	`hw <- "Hello World!"`	`hw` is a character string: `"Hello World!"`
ㅤ	Character vs numeric	`"7"`	A character string, not a number
ㅤ	ㅤ	`7`	A numeric value, usable in calculations
Vectors	Create a numeric vector	`vec1 <- c(2, 3, 5, 7)`	`[1] 2 3 5 7`
ㅤ	Combine vectors	`vec2 <- c(11, 13, 17, 19)c(vec1, vec2)`	`[1] 2 3 5 7 11 13 17 19`
ㅤ	Element-wise operations	`vec1 + vec2`	`[1] 13 16 22 26`
ㅤ	ㅤ	`vec1 + 1`	`[1] 3 4 6 8`
ㅤ	Character vector	`text.vec <- c("A", "B", "C")`	`class(text.vec)` → `"character"length(text.vec)` → `3`
ㅤ	Mixed vector	`mix.vec <- c("Hello", 3, 5)`	`[1] "Hello" "3" "5"` (coerced to character)
ㅤ	Indexing	`vec1[2]`	`[1] 3`
ㅤ	ㅤ	`vec1[c(1,4)]`	`[1] 2 7`
ㅤ	ㅤ	`vec1[-2]`	`[1] 2 5 7`
ㅤ	Replace element	`x <- 1:10; x[10] <- 99`	`x` becomes `[1] 1 2 3 4 5 6 7 8 9 99`
ㅤ	Logical condition	`x[x > 5]`	`[1] 6 7 8 9 99`
ㅤ	Logical + another vector	`y <- c(1,2,1,2,1,3,1,3,1,4)x[y == 1]`	`[1] 1 3 5 7 9` (select where `y == 1`)
matrix	Create matrix	x <- 1:10y <- c(1,2,1,2,1,3,1,3,1,4)mat1 <- cbind(x, y)	Creates a 10×2 numeric matrix mat1 with columns x and y: x y [1,] 1 1 [2,] 2 2 [3,] 3 1 ... [10,] 10 4
ㅤ	Access element	mat1[2, 1]	Gets element in row 2, column 1 → 2
ㅤ	Access column	mat1[, 2]	Gets entire second column (y): 1 2 1 2 1 3 1 3 1 4
ㅤ	Access rows	mat1[c(2, 7), ]	Gets rows 2 and 7: 2 2 7 1
ㅤ	Character matrix	cbind(c(1, 2, 3), c("A", "B", "C"))	Mixed types force all to character: [,1] [,2] [1,] "1" "A" [2,] "2" "B" [3,] "3" "C"
Data Frames	Create data frame	x <- 1:10 y <- c(1,2,1,2,1,3,1,3,1,4) df1 <-data.frame(x, y)	Creates a data frame with two columns x and y:head(df1): x y 1 1 1 2 2 2 3 3 1 ...
ㅤ	Named columns	df2 <- data.frame(var1 = x, var2 = y)	Creates data frame with columns named var1 and var2: head(df2): var1 var2 1 1 1 2 2 2 ...
ㅤ	Access elements	df1[, 2]	Accesses second column (y): [1] 1 2 1 2 1 3 1 3 1 4
ㅤ	Access elements	df1$y	Same as above: returns vector of y values
ㅤ	Access single value	df1$x[3]	Third element of column x → 3
ㅤ	Add new column	df1$z <- seq(2, 20, by = 2)	Adds new column z with even numbers: df1$z:2 4 6 8 10 12 14 16 18 20
ㅤ	Add constant column	df1$u <- 1	Adds new column u with all values equal to 1
Lists	Create a list	mylist <- list(vec1, mat1, df1) Assume: vec1 <- c(2, 3, 5, 7) mat1 <- cbind(x = 1:3, y = c(4, 5, 6)) df1 <- data.frame(a = 1:2, b = c("A", "B"))	mylist[[1]] = vec1 → 2 3 5 7 mylist[[2]] = mat1 → [,1] [,2] [1,] 1 4 [2,] 2 5 [3,] 3 6 mylist[[3]] = df1 → 2-row data frame
ㅤ	Mixed elements	person <- list(name = "Alice", scores = c(90, 85))	A named list. Access with: person$name → "Alice" person$scores → 90 85
ㅤ	Length flexibility	lengths(mylist)	Returns lengths of each element:e.g. 4 6 2 vec1 has 4 items, mat1 has 6 (3×2), df1 has 2 rows

Steps and Parameters for Creating a Barplot with `barplot()` in R

Step	Code Example / Parameter	Description	Notes
Prepare Data	`med_count <- table(Doctor$medicine)`	Create a frequency table for the variable	`table()` generates counts of each category
Call barplot()	`barplot(med_count)`	Draw the barplot	Takes a frequency table or numeric vector
Add Title	`main = "Number of Medicines Used in the Past 2 Days"`	Title of the plot	Displayed at the top of the plot window
Set X-axis Label	`xlab = "Number of Medicines"`	Label for the X-axis	Describes categories on the x-axis
Set Y-axis Label	`ylab = "Number of Individuals"`	Label for the Y-axis	Describes the height of the bars
Set Color	`col = "skyblue"`	Fill color of the bars	Can be color names or color codes
Set Border Color	`border = "black"`	Color of the bar borders	Default is black; can be changed or removed
Other Parameters	`las`, `beside`, `space`, `ylim`, etc.	Axis label rotation, grouped bars, spacing, axis limits	Advanced customization options