FREE MATLAB Data Import and Visualization Questions and Answers

Question 1

A data analyst has a CSV file named 'sensor_data.csv' with mixed data types (numbers and text) and a header row. Which function is most suitable for importing this data into MATLAB as a table, preserving the data types and using the header for variable names?

Accepted Answer

readtable('sensor_data.csv')

Answer

The `readtable` function is specifically designed to import tabular data from files like CSVs. It automatically detects headers, parses columns with different data types, and organizes the data into a table, which is ideal for mixed data types. `readmatrix` is best for purely numeric data, `load` is for MAT-files, and `readcell` imports into a cell array without the structured benefits of a table.

Question 2

A user has imported data into a table named `patientData`. The table has variables named 'LastName', 'Age', and 'BloodPressure'. How can the user extract all values from the 'Age' column into a standard numeric vector?

Accepted Answer

patientData.Age

Answer

Dot notation (`tableName.variableName`) is a direct and efficient way to access the data within a single table variable, returning it as a standard MATLAB array of the appropriate data type. Using parentheses `()` would return a new table containing just the 'Age' column, while curly braces `{}` can also extract the data but dot notation is often more readable for a single variable.

Question 3

Which of the following commands will create a plot of `y` versus `x` with a red, dashed line and circular markers?

Accepted Answer

plot(x, y, 'r--o')

Answer

The `plot` function accepts a character vector or string, often called a `LineSpec`, to define the line style, color, and marker. In 'r--o', 'r' specifies red, '--' specifies a dashed line, and 'o' specifies circular markers. The other options use incorrect syntax or combine `LineSpec` characters with Name-Value pairs improperly.

Question 4

A researcher needs to save a figure currently displayed on the screen to a high-resolution PNG file named 'figure1.png' for publication. Which command is most appropriate for this task?

Accepted Answer

exportgraphics(gcf, 'figure1.png', 'Resolution', 300)

Answer

`exportgraphics` is the modern and recommended function for saving figures to various formats with control over properties like resolution. Using `exportgraphics(gcf, 'figure1.png', 'Resolution', 300)` saves the current figure (`gcf`) as a PNG with a resolution of 300 DPI. While `print` can also achieve this, `exportgraphics` offers a more streamlined syntax. `savefig` saves as a .fig file, and `save` is for workspace variables.

Question 5

A user wants to create a stacked bar chart from a numeric matrix `data`, where each column of `data` represents a category and each row represents a series. Which command correctly generates a stacked bar chart?

Accepted Answer

bar(data, 'stacked')

Answer

To create a stacked bar chart, you use the `bar` function and provide the `'stacked'` option as an additional argument. This tells MATLAB to stack the values from each row within the same bar for each column. The other functions or options are not valid MATLAB syntax for creating a stacked bar chart.

MATLAB - MATLAB Technical Computing Practice Test

MATLAB - MATLAB Technical Computing Practice Test

FREE MATLAB Data Import and Visualization Questions and Answers