Simple Data Frame Tutorial

This is a simple tutorial where a csv document is read and will perform some data slicing operations to access specific data.

IRIS dataset from “http://vincentarelbundock.github.io/Rdatasets/csv/datasets/iris.csv” is read into data1. Let us copy only first 15 rows into irdata using slicing irdata <- data1[1:15,] names(irdata) displays the header of the data

data1 <- read.csv("http://vincentarelbundock.github.io/Rdatasets/csv/datasets/iris.csv",header=TRUE,sep=",") 
irdata <- data1[1:15,]
names(data1)

## [1] "X"            "Sepal.Length" "Sepal.Width"  "Petal.Length"
## [5] "Petal.Width"  "Species"

names(irdata)

## [1] "X"            "Sepal.Length" "Sepal.Width"  "Petal.Length"
## [5] "Petal.Width"  "Species"

Row Slicing

1. Get data from 1^st to 10^th rows in irdata (Also, c(1:10) and 1:10 gives a vector of 1 2 3 4 5 6 7 8 9 10)

c(1:10)

##  [1]  1  2  3  4  5  6  7  8  9 10

1:10

##  [1]  1  2  3  4  5  6  7  8  9 10

irdata[1:10,]

##     X Sepal.Length Sepal.Width Petal.Length Petal.Width Species
## 1   1          5.1         3.5          1.4         0.2  setosa
## 2   2          4.9         3.0          1.4         0.2  setosa
## 3   3          4.7         3.2          1.3         0.2  setosa
## 4   4          4.6         3.1          1.5         0.2  setosa
## 5   5          5.0         3.6          1.4         0.2  setosa
## 6   6          5.4         3.9          1.7         0.4  setosa
## 7   7          4.6         3.4          1.4         0.3  setosa
## 8   8          5.0         3.4          1.5         0.2  setosa
## 9   9          4.4         2.9          1.4         0.2  setosa
## 10 10          4.9         3.1          1.5         0.1  setosa

2. Get 2^nd, 5^th, 7^th rows from irdata

irdata[c(2,5,7),]

##   X Sepal.Length Sepal.Width Petal.Length Petal.Width Species
## 2 2          4.9         3.0          1.4         0.2  setosa
## 5 5          5.0         3.6          1.4         0.2  setosa
## 7 7          4.6         3.4          1.4         0.3  setosa

3. Get a 4^th row from irdata

irdata[4,]

##   X Sepal.Length Sepal.Width Petal.Length Petal.Width Species
## 4 4          4.6         3.1          1.5         0.2  setosa

Column Slicing

1. Get data from 1^st to 4^th columns in irdata irdata[1:4] and irdata[,1:4] returned same data

c(1:4)

## [1] 1 2 3 4

1:4

## [1] 1 2 3 4

irdata[1:4]

##     X Sepal.Length Sepal.Width Petal.Length
## 1   1          5.1         3.5          1.4
## 2   2          4.9         3.0          1.4
## 3   3          4.7         3.2          1.3
## 4   4          4.6         3.1          1.5
## 5   5          5.0         3.6          1.4
## 6   6          5.4         3.9          1.7
## 7   7          4.6         3.4          1.4
## 8   8          5.0         3.4          1.5
## 9   9          4.4         2.9          1.4
## 10 10          4.9         3.1          1.5
## 11 11          5.4         3.7          1.5
## 12 12          4.8         3.4          1.6
## 13 13          4.8         3.0          1.4
## 14 14          4.3         3.0          1.1
## 15 15          5.8         4.0          1.2

irdata[,1:4]

##     X Sepal.Length Sepal.Width Petal.Length
## 1   1          5.1         3.5          1.4
## 2   2          4.9         3.0          1.4
## 3   3          4.7         3.2          1.3
## 4   4          4.6         3.1          1.5
## 5   5          5.0         3.6          1.4
## 6   6          5.4         3.9          1.7
## 7   7          4.6         3.4          1.4
## 8   8          5.0         3.4          1.5
## 9   9          4.4         2.9          1.4
## 10 10          4.9         3.1          1.5
## 11 11          5.4         3.7          1.5
## 12 12          4.8         3.4          1.6
## 13 13          4.8         3.0          1.4
## 14 14          4.3         3.0          1.1
## 15 15          5.8         4.0          1.2

2. Get 2^nd, 4^th, 6^th columns from irdata

irdata[c(2,4,6)]

##    Sepal.Length Petal.Length Species
## 1           5.1          1.4  setosa
## 2           4.9          1.4  setosa
## 3           4.7          1.3  setosa
## 4           4.6          1.5  setosa
## 5           5.0          1.4  setosa
## 6           5.4          1.7  setosa
## 7           4.6          1.4  setosa
## 8           5.0          1.5  setosa
## 9           4.4          1.4  setosa
## 10          4.9          1.5  setosa
## 11          5.4          1.5  setosa
## 12          4.8          1.6  setosa
## 13          4.8          1.4  setosa
## 14          4.3          1.1  setosa
## 15          5.8          1.2  setosa

irdata[,c(2,4,6)]

##    Sepal.Length Petal.Length Species
## 1           5.1          1.4  setosa
## 2           4.9          1.4  setosa
## 3           4.7          1.3  setosa
## 4           4.6          1.5  setosa
## 5           5.0          1.4  setosa
## 6           5.4          1.7  setosa
## 7           4.6          1.4  setosa
## 8           5.0          1.5  setosa
## 9           4.4          1.4  setosa
## 10          4.9          1.5  setosa
## 11          5.4          1.5  setosa
## 12          4.8          1.6  setosa
## 13          4.8          1.4  setosa
## 14          4.3          1.1  setosa
## 15          5.8          1.2  setosa

3. Get a 4^th column from irdata

irdata[4]

##    Petal.Length
## 1           1.4
## 2           1.4
## 3           1.3
## 4           1.5
## 5           1.4
## 6           1.7
## 7           1.4
## 8           1.5
## 9           1.4
## 10          1.5
## 11          1.5
## 12          1.6
## 13          1.4
## 14          1.1
## 15          1.2

irdata[,4]

##  [1] 1.4 1.4 1.3 1.5 1.4 1.7 1.4 1.5 1.4 1.5 1.5 1.6 1.4 1.1 1.2

Combining Row and Column Slicing

1. Get 3^rd, 5^th columns of 2^nd,4^th,10^th,12^th rows of irdata

irdata[c(2,4,10,12),c(3,5)]

##    Sepal.Width Petal.Width
## 2          3.0         0.2
## 4          3.1         0.2
## 10         3.1         0.1
## 12         3.4         0.2