Top 30 MATLAB Interview Questions with Answers

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Sure! Here are the top 30 MATLAB interview questions with their answers:

1. What is MATLAB?

MATLAB stands for “MATrix LABoratory.” It is a high-level programming language and environment designed for numerical computation, data analysis, and visualization.

2. What are the key features of MATLAB?

Some key features of MATLAB include a large library of mathematical functions, powerful plotting and visualization capabilities, matrix manipulation, algorithm development, and toolboxes for various application areas.

3. How do you create a vector in MATLAB?

You can create a vector in MATLAB using square brackets ([]), separating the elements with commas or spaces. For example : x = [1, 2, 3] or x = [1 2 3].

4. What is the difference between a script file and a function file in MATLAB?

A script file contains a sequence of MATLAB commands that are executed in the order they appear. A function file, on the other hand, is a separate file that defines a function, which can be called with arguments and returns values.

5. How do you comment in MATLAB?

MATLAB uses the percent sign (%) to indicate a comment. Anything written after the percent sign on a line is considered a comment and is ignored by the interpreter.

6. How can you access a specific element of a matrix in MATLAB?

In MATLAB, you can access a specific element of a matrix using indexing. For example, to access the element at the second row and third column of matrix A, you can use A(2, 3).

7. How do you calculate the mean of a vector in MATLAB?

MATLAB provides the mean function to calculate the mean of a vector. For example, to calculate the mean of vector x, you can use mean(x).

8. What is the difference between element-wise multiplication and matrix multiplication in MATLAB?

Element-wise multiplication in MATLAB is performed using the .* operator and multiplies the corresponding elements of two matrices. Matrix multiplication is performed using the * operator and follows the rules of linear algebra.

9. How do you generate a random number in MATLAB?

MATLAB provides the rand function to generate a random number between 0 and 1. For example, x = rand.

10. What is the difference between a global variable and a local variable in MATLAB?

A global variable in MATLAB can be accessed and modified from anywhere in the program. A local variable, on the other hand, is defined within a function and can only be accessed within that function.

11. What is the type of program files that MatLab allows to write?

Matlab allows two types of program files

  • Scripts: It is a file with a .m extension. In these files, it writes a series of commands that you want to execute together. It does not accept inputs and does not return any outputs
  • Functions: They are also files with .m extension. Functions can accept inputs and return outputs.

12. Explain how to modify the MatLab Path?

To modify the MatLab Path use the PathTool GUI. Also, you can use add path directories from the command line and add the path to rc to write the current path back to ‘pathdef.m.’ In the case if you don’t have permission to write for ‘pathdef.m’ then pathrc can be written into a different file, you can execute from your ‘startup.m.’

13. Explain what is LaTex in MatLab?

MatLab handles naturally simple LaTex encoding which allows introducing greek letters or modifying the font size and appearance in plots.

14. Explain how you can pre-allocate a Non-Double Matrix?

Pre-allocating a block of memory for holding a non-double matrix is memory efficient. While allocating blocks of memory for a matrix, zeros are pre-allocated to a matrix. The functions to pre allocate memory is int8(), example matrix =int8(zeros(100)); Repmat function is used to create a single double matrix, example matrix2=repmat(int8(0), 100, 100)

15. What is Xmath-Matlab? Mention the Xmath features?

For Xwindow workstations, Xmath is an interactive scripting and graphics environment. Following are the X-math features

  • Scripting language with OOP features
  • Libraries that are LNX and C language compatible
  • A debugging tool with GUI features
  • Color graphics can be pointed and clickable

16. Name the graphic system used in MatLab?

The graphic system used in MatLab is known as handle graphics. It has high-level and low-level commands.

  • High-Level Commands: High-level command performs image processing, data visualization, and animation for 2D and 3D presentation graphics
  • Low-Level Commands: Full customization of the appearance of graphics and building of a complete graphical user interface

17. Explain what is M-file and MEX files in MatLab?

M files: They are just plain ASCII text that is interpreted at run time. They are like sub-programs stored in text files with .m extensions and are called M-files. For most of the MatLab, development M-files are used. MEX files: They are basically native C or C++ files that are linked directly to the MatLab application at runtime. MEX files have the efficiency to crash the MatLab application.

18. Explain what is Interpolation and Extrapolation in Matlab? What are their types?

  • Interpolation: Taking out function values between different data points in an array is referred to as Interpolation
  • Extrapolation: Finding function values beyond the endpoints in the array is referred to as Extrapolation

The two types of Interpolation and Extrapolation are

  • Linear Interpolation and Extrapolation
  • Quadratic Interpolation and Extrapolation

19. List out some of the common toolboxes present in Matlab?

Some of the common toolboxes in Matlab are

  • Control System
  • Fuzzy Logic
  • Image Processing
  • LMI control
  • Neural Networks
  • Robust Control
  • System Identification

20. What is Get and Set in Matlab?

Get and Set are referred as getter and setter functions. For assigning properties, setter functions are used while for accessing properties getter functions are used.

21. How can an SVM (Support Vector Machine) be implemented in MATLAB?

A Support Vector Machine (SVM) in MATLAB is a supervised machine learning algorithm that developers can utilise for various classification problems such as signal processing in medical applications, Natural Language Processing (NLP) and image and speech recognition. The SVM algorithm is designed to separate the data points in one class from the points of another class as much as possible.

The support vectors in an SVM are the subset of the training observations that help in identifying the location of the separating hyperplane. The algorithm can be implemented in programs written for detecting anomalies using an outlier threshold on objects.

If data contains exactly two classes, an SVM can be used to classify the data by finding the best hyperplane that has the largest margin between the two classes. SVMs can typically be used to work on separable data, non-separable data and non-linear transformation with kernels. The classifier can be trained, tuned and used to classify new data.

22. How can audio files be read in MATLAB?

The syntax for reading audio files in MATLAB is of three kinds, depending on the information to be read by the user:

Reading the Sample Data and Sample Rate
[y,Fs] = audioread(filename)

The function ‘audioread’ is used to read the data from the file named ‘filename’. The sampled data is returned through the variable ‘y’ and the sample rate for the data through ‘Fs’.

Reading a selected range of audio samples
[y,Fs] = audioread(filename, samples)

The function ‘samples’ is a vector of the form [start, finish], where ‘start’ and ‘finish’ refer to the first and last samples to read. These values are positive scalar integers. The two values should be lesser than the number of audio samples.

Reading the sampled data in the data range of the ‘native’ or ‘double’ type.
[y,Fs] = audioread(__, datatype)

The format of the data read will be with normalised samples or else samples in the native format.

The variable ‘y’ typically contains the audio data in a matrix form ‘m by n’. The variable ‘m’ is the number of audio samples read, and ‘n’ is the number of audio channels. The default datatype of ‘y’ is double.

23. What types of loops are provided by MATLAB?

Similar to other programming languages, MATLAB provides three types of loops such as:

1) For loop: This loop is used to repeat a procedure a specified number of times.

The syntax is-
for index = values

2) While loop: This loop is used to repeat itself when the condition is true.

The syntax is-
while expression

The group of statements written in this loop at executed as long as the expression is proven true. A true event occurs when the result contains non-zero elements.

3) Nested loops: These loops are used to run one loop within another loop. The nested loop can run a fixed number of iterations of the inner loop and stop the outer loop upon satisfying a particular condition.
The syntax is-
for I = 1 : 3
for j = 1 : 3
fprintf(‘i=%d, j=%d/n’, I, j);

The outer loop iteratively runs the values of ‘i’ from 1 to 3, and the inner loop iteratively runs the values of ‘j’ from 1 to 3. The whole loop body prints the message that includes the values of ‘i’ and ‘j’.

24. How can a P-code in MATLAB be described?

P-codes are a method to secure MATLAB source codes so that others will not have access to them in any project. A MATLAB file has the extension ‘.m’, whereas the extension of a p-code in MATLAB is ‘.p’. The p-code file is executed the same as the MATLAB source file. When a source file is p-coded in MATLAB, it is obfuscated to hide the original data, where the data becomes confusing to interpret.

Obfuscation turns files into proprietary formats and can be used with the ‘pcode’ function as follows:

pcode file1, file2,….

The above command generates the P-code files like ‘filename.p’.

pcode *.m
The above command converts all the source ‘.m’ files to P-code files.

25. How can polynomials be written in MATLAB?

Polynomials are mathematical equations containing one variable with non-negative integer components. The MATLAB environment expresses polynomials using numeric row vectors that contain the coefficients of the polynomial. The coefficients are typically ordered by descending power.

For example, a numeric vector with three-four elements can be expressed as:

P = [p3 p2 p1 p0];

This vector can be represented as a polynomial, such as:
p(x) = px3 + px2 + px + p

The vector can be written with example values as follows:
p = [1 –2 2];

26. What are MEX files in MATLAB?

A MEX file in MATLAB is a function used to call a C or C++ program or a Fortran routine. Short for ‘MATLAB Executable’, mex files can be called from the command line in MATLAB like built-in functions. This file type is to be carefully used only when required as it is time-consuming and low-level in nature. Users can build their written programs using the ‘mex’ command.

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27. Can programs be run on MATLAB without graphics?

In the case of a slow internet connection, users can start MATLAB without any graphics involved by using either of the following commands:
“matlab -nodesktop –dodisplay”

28. What are the Get and Set functions in MATLAB?

Graphic objects in MATLAB implement interfaces based on ‘set’ and ‘get’ functions. These functions allow access to various properties on object arrays when a function is called. The getter functions are used to access features, and the setter functions are used for assigning properties to objects.

29. What is Latex in MATLAB?

Latex, referred to as ‘LaTeX’ is a system intended to prepare documents for publishing scientific documents. LaTeX allows users to write in plain text instead of formatted text in Microsoft Word.

LaTeX can be used to express symbols in MATLAB with the command: “chr = latex(S)”

30. How can the path be modified in MATLAB?

Users can modify the path in MATLAB using the ‘PathTool GUI’. They can also add more directories to the path from the command line. If users do not have permission to write for the command ‘pathdef.m’ then ‘pathrc’ can be written in a different file.

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