In this homework, we will make a scatter plot using R on the mtcars dataset.

  1. Load the dataset using code provided in the Rscript hw2.R.
  2. Obtain basic summary statistics.
  3. Make a plot using the provided code. Explain what the pch, col options do in the plot command. Explore changes to these options and their effects.
  4. Complete your homework using RMarkdown below, turn in your Rmd file and final rendered report.

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= R code to produce a mtcars plot =

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1. load libraries and dataset

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the datasets library contains many datasets

use help(package = "datasets") to list them all

library("datasets")

# RColorBrewer contains useful color palettes
# use `display.brewer.all()` to see all palettes
library("RColorBrewer")

# load mtcars
# mtcars is a dataset of 32 cars with different attributes
# use `?mtcars` to see the details
data(mtcars)
# use `attach` for faster access of variables
attach(mtcars)

2. make graph

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plot(wt, mpg, pch = c(15, 16, 15, 15, 15), col = factor(cyl))

# add legend
legend("topright", legend = c("manual", "automatic", "cyl = 4", "cyl = 6", "cyl = 8"), pch = c(15, 16, 15, 15, 15), col = c(1, 1, 1, 2, 3))

Parameters in the plot command:
pch: a vector of plotting characters or symbols. In other words, it uses a numerical code to assign a symbol to corresponding points in the plot.
col: assigns a color to the points of interest

4. Summary statistics

summary(mtcars)
##       mpg             cyl             disp             hp       
##  Min.   :10.40   Min.   :4.000   Min.   : 71.1   Min.   : 52.0  
##  1st Qu.:15.43   1st Qu.:4.000   1st Qu.:120.8   1st Qu.: 96.5  
##  Median :19.20   Median :6.000   Median :196.3   Median :123.0  
##  Mean   :20.09   Mean   :6.188   Mean   :230.7   Mean   :146.7  
##  3rd Qu.:22.80   3rd Qu.:8.000   3rd Qu.:326.0   3rd Qu.:180.0  
##  Max.   :33.90   Max.   :8.000   Max.   :472.0   Max.   :335.0  
##       drat             wt             qsec             vs        
##  Min.   :2.760   Min.   :1.513   Min.   :14.50   Min.   :0.0000  
##  1st Qu.:3.080   1st Qu.:2.581   1st Qu.:16.89   1st Qu.:0.0000  
##  Median :3.695   Median :3.325   Median :17.71   Median :0.0000  
##  Mean   :3.597   Mean   :3.217   Mean   :17.85   Mean   :0.4375  
##  3rd Qu.:3.920   3rd Qu.:3.610   3rd Qu.:18.90   3rd Qu.:1.0000  
##  Max.   :4.930   Max.   :5.424   Max.   :22.90   Max.   :1.0000  
##        am              gear            carb      
##  Min.   :0.0000   Min.   :3.000   Min.   :1.000  
##  1st Qu.:0.0000   1st Qu.:3.000   1st Qu.:2.000  
##  Median :0.0000   Median :4.000   Median :2.000  
##  Mean   :0.4062   Mean   :3.688   Mean   :2.812  
##  3rd Qu.:1.0000   3rd Qu.:4.000   3rd Qu.:4.000  
##  Max.   :1.0000   Max.   :5.000   Max.   :8.000