MatLab

AddNoiseData.m

%% Script to read in 2D array of grade data

% Also provides column names

dataN = csvread('DataClass.csv');

strColumns = {'LabQuiz', 'zyBooks', ...

'Labs', 'Homeworks', ...

'MidtermI', 'MidtermII', 'Final', ...

'ExamAverage', 'Grade'};

% Line styles

strLineStyles = {'--b', ':b', '-k', '--k', ':g', '--g', '.g', '-g', '-r'};

%% Add noise to the data (+- 1) and write it out

% rand generates a 2D array of noise in the range of 0 to 1

% shift and scale

noise = 2 * (rand( size(dataN) ) - 1.0);

dataN = dataN + noise;

csvwrite('DataClassWithNoise.csv', dataN)

Already finish problem 1, need help for problem 2.

Problem 1

Plot last years ENGR112 data by type.

Deliverables:

Plot of data

Each type of data

Lines for grade divisions (70, 80, 90)

Legend

Script

Command window output

Step by Step Instructions:

Start a new script and copy the first lines from AddNoiseData.m (the ones that read in the data and create the string arrays that say what the column headers are and provide colors for the plot.

Run and make sure that you are reading data correctly what size is dataN?

Plot one column of data

colData = dataN(:, 1); % Gets the first column of the data

What happens if you just plot it? Try plotting it with markers

You want sort().

Sort the data and plot it.

In this case you dont need to make a dependent variable t. You can just call plot( colData, -b) and it will default to plotting 0, 1, 2, etc

Wrap the code for the bit above in a for loop

Remember that size( dataN, 2 ) will give you the number of columns to plot over

Remember to change 1 to your loop index variable

Pretty colors

You can use the strLineStyles to set a different color for each plot. Remember to use {}

You can use the strColumns in the legend as-is; to put the legend in the upper left hand corner, use the Location option (google matlab legend).

Adding the horizontal stripesUse a for loop to plot one stripe at 70, one at 80, one at 90. Remember that the x values start at 0 and go to the number of students == number of rows.

plot( [xStart, xEnd], [height, height], -r );

Problem 2

Print out the following statistics from the data in problem 1:

Number of students who did better on the labs than the homeworks

Number of students who did better on the homeworks than the final exam

Average score for each category

[Extra credit] Average difference between labs & homeworks and homeworks & final exam

[Extra credit] Do the number counts with relational operators. You can calculate those numbers with a single line of code

Deliverables:

Script for calculating the above

Command window output

Must use for loops

Step by Step Instructions:

Copy the first few lines from your Lab 1 problem (reading dataN and the strColumns)

Printing out the means of each columnThere are two ways to do this:

One is to call mean with the entire matrix (refer to help on mean to see what will happen when you do this

Use the colon operator to get out all of the elements for the column IN the for loop and then call mean on that (column) array.

Either way youll need a for loop that goes over each column (use size() command)

Use strColumns to print out the name of the column along with the mean

Note: The first method is more efficient.

Counting studentsFirst thing to do is declare an index variable for each of the columns youre interested in; that way, if they change later you dont have to re-write your code. Also makes it easier to read the code

indexLabColumn = 3;

Create a for loop that goes over each STUDENT this time (i.e., number of rows)

Make a counting variable, eg, betterLabThanHomework = 0;

Do just the homework score better than the lab score first. Hint: Youll need an if statement in the for loop

If youre struggling with either how to write the if or how to increment the counter variable, grab a TA

Add another if statement for the homeworks and exams

Extra credit IThis should look like mean( lab homework ) how do you get out ALL of the student lab scores all at once? Hint: colon operator

You should do this without a for loop for credit.

Extra credit IIThis should look like sum( lab > homework ) and like extra credit I you want to perform the comparison on ALL of the students all at once (not using a for loop)

lab > homework will return an ARRAY of zeros and ones, zeros for false, ones for true. Then just count the ones

Self-check:

Average 82.X4 for item LabQuiz

Average 135.X2 for item zyBooks

Average 93.X0 for item Labs

Average 91.X9 for item Homeworks

Average 80.X1 for item MidtermI

Average 75.X9 for item MidtermII

Average 65.X6 for item Final

Average 73.X9 for item ExamAverage

Average 86.X4 for item Grade

Number of people with lab scores higher than homeworks: 1X5

Average difference: 1.X0

Number of people with homework scores higher than final exam: 2X5

Average difference: 25.X3

Total number of students: 2X9