Homework

Ilina

mydata <- data.frame("ID" = c( 1,2,3), 
                     "Age" = c(24, 28, 30), 
                     "Gender" = c("M", "F", "F"))#Manually inserting the data

I would like to create new dataset, including only ID and Age (below in the bracket [ ]what i write before the comma it goes for rows and after the comma it goes for columns)

mydata2 <- mydata[ ,-3] #Deleting the third column

Create mydata3, including only first row of data

mydata3 <- mydata [1 , ]
mydata[1,2] <- 22 #Changing particular value in a data frame

Take mydata and insert a new variable, called Height, with values 180, 170, 172

mydata$Height <- c(180, 170, 172)
print (mydata)
##   ID Age Gender Height
## 1  1  22      M    180
## 2  2  28      F    170
## 3  3  30      F    172

Create new variable, called HeightNew, which increases each student by 2 cm

mydata$Height1 <- mydata$Height + 2
print (mydata)
##   ID Age Gender Height Height1
## 1  1  22      M    180     182
## 2  2  28      F    170     172
## 3  3  30      F    172     174
summary (mydata [ ,c(-1,-3)])
##       Age            Height       Height1   
##  Min.   :22.00   Min.   :170   Min.   :172  
##  1st Qu.:25.00   1st Qu.:171   1st Qu.:173  
##  Median :28.00   Median :172   Median :174  
##  Mean   :26.67   Mean   :174   Mean   :176  
##  3rd Qu.:29.00   3rd Qu.:176   3rd Qu.:178  
##  Max.   :30.00   Max.   :180   Max.   :182

Explanation of results: q1: 25 Range for Height: 10 cm Interq. range for Age: q3-q1 = 29 - 25 = 4

mean(mydata$Age)
## [1] 26.66667

standard deviation in R

sd(mydata$Height)
## [1] 5.291503

we would like yo use function, called describe. First, we need to install library psych

#install.packages("psych")
library(psych)
describe(mydata[ , c(-1, -3) ])
##         vars n   mean   sd median trimmed  mad min max range  skew
## Age        1 3  26.67 4.16     28   26.67 2.97  22  30     8 -0.29
## Height     2 3 174.00 5.29    172  174.00 2.97 170 180    10  0.32
## Height1    3 3 176.00 5.29    174  176.00 2.97 172 182    10  0.32
##         kurtosis   se
## Age        -2.33 2.40
## Height     -2.33 3.06
## Height1    -2.33 3.06