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Berkeley STAT 133 - Traffic flow on highways in California

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Stat 133, Fall ’06Homework 1: R IntroductionDue 6 pm Friday, 8 SepTraffic flow on highways in CaliforniaThe data available for this lab assignment can be found on the web atwww.stat.berkeley.edu/users/nolan/stat133/data/flow-occ-table.txtThese data have been collected by loop detectors at one particular location of eastbound Interstate80 in Sacramento, California. There are six columns and 1740 rows in the data set. The rowscorrespond to successive five minute intervals from March 14 to 20, 2003, where the data values ina row report the flow (number of cars) and occupancy (the proportion of time there was a car overthe loop) in each of three lanes on the freeway. Lane 1 is the leftmost lane, lane 2 is in the center,and lane 3 is the rightmost. The original data are from the Freeway Performance MeasurementSystem (PEMS) websitehttp://pems.eecs.berkeley.edu/Public/Your tasks for this assignment are to:• Read the data directly from the web into R using one of the R functions readLines, read.table,read.csv, or scan. Do not download the data to your computer as a txt file before reading itinto R. Explain in one sentence the reason for choosing the function that you did for readingthe data into R.• Explore the data visually to answer the following questions1:1. Examine the relationships of the flows in the three lanes using boxplots. Is the state-ment, “The flow in lane 2 is typically about 50% higher than in lane 3,” an accuratedescription of the relationship you found? Explain in one sentence.2. Consider the flows in the three lanes using time series plots. Which lane typically servesthe most traffic? Is the statement, “When one lane is congested, the others are too,” anaccurate description of the relationship you found?1These questions are derived from those supplied by John Rice, Dept. Statistics, U.C. Berkeley13. Consider the relationship between flow and occupancy. Plot flow against occupancy forlane 1. In one sentence, describe the shape of the points. Relate the shape you see toa propoerty of traffic. Is this relationship born out in the other two lanes. Explain anysimilarities and differences that you find.Consider using the R functions plot, boxplot, density, hist, pairs, and points. Also considerusing some of the arguments to the plotting functions to improve the appearance of your plot,such as ylim, xlab, main, log, type, col, and lwd.Submit for grading your• Paragraph of findings.• One plot for each of the above questions.• The commands used to conduct your analysis.Your submission should be contained in a single pdf file. If for example, the report is composedin Word as a doc file that contains the written paragraph, code, and plots, then you will need toprint it to a pdf file before submitting it.Submit this HW via bspace, and turn in a hard copy in class on Monday, Sep


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