Bar and histogram plots in MATLAB - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a simple bar plot of the data vector.

MATLAB

data = [5, 10, 15, 20];
bar([1]);

Drag options to blanks, or click blank then click option'

Aplot

Bhistogram

Cdata

Dscatter

Attempts:

3 left

💡 Hint

Common Mistakes

Using plot instead of bar function input.

Using histogram function inside bar function.

Passing a function name instead of data.

The bar function in MATLAB takes the data vector as input to create a bar plot.

2fill in blank

medium

Complete the code to create a histogram with 10 bins for the data vector.

MATLAB

data = randn(100,1);
histogram(data, [1]);

Drag options to blanks, or click blank then click option'

A10

B5

C20

D50

Attempts:

3 left

💡 Hint

Common Mistakes

Using too few or too many bins causing unclear histogram.

Passing a vector instead of a scalar for bins.

The second argument to histogram specifies the number of bins. Here, 10 bins are requested.

3fill in blank

hard

Fix the error in the code to correctly plot a bar chart with categories.

MATLAB

categories = {'A', 'B', 'C'};
values = [10, 20, 15];
bar(categorical([1]), values);

Drag options to blanks, or click blank then click option'

Avalues'

Bvalues

C1:3

Dcategories

Attempts:

3 left

💡 Hint

Common Mistakes

Using a numeric vector like 1:3, which results in default numeric labels.

Using values as the x-axis input.

The bar function accepts a categorical array as the first input to set the x-axis labels to those categories (A, B, C).

4fill in blank

hard

Fill both blanks to create a histogram with 15 bins and set the face color to red.

MATLAB

data = randn(200,1);
h = histogram(data, [1]);
h.FaceColor = [2];

Drag options to blanks, or click blank then click option'

A15

B10

C'red'

D'blue'

Attempts:

3 left

💡 Hint

Common Mistakes

Using color without quotes.

Setting bins to a wrong number.

The first blank sets the number of bins to 15. The second blank sets the bar color to red using a string.

5fill in blank

hard

Fill all three blanks to create a bar plot with custom x labels and set the bar color to green.

MATLAB

values = [3, 7, 5];
categories = {'X', 'Y', 'Z'};
bar(1:3, values, 'FaceColor', [1]);
set(gca, 'XTickLabel', [2]);
title([3]);

Drag options to blanks, or click blank then click option'

A'red'

B'green'

Ccategories

D'My Bar Plot'

Attempts:

3 left

💡 Hint

Common Mistakes

Using color without quotes.

Passing numeric vector instead of cell array for XTickLabel.

Forgetting quotes around title string.

The bar color is set to green with 'green'. The x-axis labels are set to the categories cell array. The plot title is set with a string.

Practice

1. Which of the following best describes the difference between a bar plot and a histogram in MATLAB?

easy

A. Both bar plots and histograms display values for specific categories.

B. Bar plots show data distribution over ranges; histograms display values for specific categories.

C. Both bar plots and histograms show data distribution over ranges.

D. Bar plots display values for specific categories; histograms show data distribution over ranges.

Solution

1. Step 1: Understand bar plot purpose

   Bar plots show values for distinct categories or positions, like sales per month.

2. Step 2: Understand histogram purpose

   Histograms group data into ranges (bins) to show how data spreads, like exam scores distribution.

3. Final Answer:

   Bar plots display values for specific categories; histograms show data distribution over ranges. -> Option D

4. Quick Check:

   Bar = categories, Histogram = ranges [OK]

Hint: Bar = categories, Histogram = data spread [OK]

Common Mistakes:

• Confusing bar plots with histograms
• Thinking both show the same type of data
• Assuming histograms show exact values per category

2. Which MATLAB command correctly creates a bar plot for the vector y = [3, 7, 5]?

easy

A. bar(y)

B. histogram(y)

C. plotbar(y)

D. barplot(y)

Solution

1. Step 1: Identify correct function for bar plot

   The MATLAB function to create a bar plot is bar().

2. Step 2: Check syntax correctness

   Calling bar(y) plots the values in vector y as bars.

3. Final Answer:

   bar(y) -> Option A

4. Quick Check:

   Use bar() for bar plots [OK]

Hint: Use bar() to plot bar charts, histogram() for histograms [OK]

Common Mistakes:

• Using histogram() instead of bar()
• Using non-existent functions like plotbar()
• Incorrect function names or typos

3. What will be the output of the following MATLAB code?

data = [1, 2, 2, 3, 3, 3, 4];
histogram(data, 3)

medium

A. An error because histogram requires vector of edges

B. A histogram with 3 bins showing counts of data in ranges covering 1 to 4

C. A bar plot with bars at positions 1, 2, 3, 4

D. A line plot connecting the data points

Solution

1. Step 1: Understand histogram function with bin count

   Calling histogram(data, 3) creates a histogram with 3 bins dividing the data range.

2. Step 2: Analyze data distribution

   Data ranges from 1 to 4, so bins cover intervals like [1-2), [2-3), [3-4]. Counts show how many values fall in each bin.

3. Final Answer:

   A histogram with 3 bins showing counts of data in ranges covering 1 to 4 -> Option B

4. Quick Check:

   histogram(data, bins) = bins count [OK]

Hint: histogram(data, n) makes n bins for data spread [OK]

Common Mistakes:

• Confusing histogram with bar plot output
• Expecting exact bars at data points
• Thinking histogram needs edges vector always

4. The following MATLAB code is intended to create a bar plot of y = [4, 6, 8], but it produces an error. What is the error?

bar y

medium

A. Incorrect function name; should be histogram

B. Vector y is not defined

C. Missing parentheses around the vector argument

D. bar function cannot plot vectors

Solution

1. Step 1: Check syntax of bar function call

   The correct syntax requires parentheses: bar(y).

2. Step 2: Identify cause of error

   Writing bar y without parentheses causes MATLAB syntax error.

3. Final Answer:

   Missing parentheses around the vector argument -> Option C

4. Quick Check:

   Function calls need parentheses [OK]

Hint: Always use parentheses when calling functions [OK]

Common Mistakes:

• Omitting parentheses in function calls
• Confusing bar with histogram function
• Assuming vector y is undefined without checking

5. You have a dataset of exam scores: scores = [55, 70, 70, 85, 90, 90, 90, 100]. You want to create a histogram with bins of width 10 (like 50-59, 60-69, etc.). Which MATLAB command correctly creates this histogram?

hard

A. histogram(scores, 'BinWidth', 10)

B. bar(scores, 10)

C. histogram(scores, 10)

D. bar(scores, 'BinWidth', 10)

Solution

1. Step 1: Understand how to set bin width in histogram

   Use histogram(data, 'BinWidth', value) to specify bin size.

2. Step 2: Check options for correct syntax

   histogram(scores, 'BinWidth', 10) uses correct syntax to set bin width to 10 for scores.

3. Step 3: Identify incorrect options

   Options B and D use bar function incorrectly; C sets number of bins, not width.

4. Final Answer:

   histogram(scores, 'BinWidth', 10) -> Option A

5. Quick Check:

   Use 'BinWidth' to set histogram bin size [OK]

Hint: Use 'BinWidth' property to set histogram bin size [OK]

Common Mistakes:

• Using bar instead of histogram for bin width
• Passing number instead of 'BinWidth' name-value pair
• Confusing bin count with bin width