multiple assignment matlab

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Assign Multiple Variables

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How to Assign Multiple Variables in MATLAB in One Line

How to Assign Multiple Variables at Once in MATLAB

MATLAB is a powerful programming language for engineers and scientists. It’s known for its fast, efficient, and easy-to-use syntax. One of the things that makes MATLAB so popular is its ability to assign multiple variables at once. This can save you a lot of time and effort, especially when you’re working with large datasets.

In this article, we’ll show you how to assign multiple variables at once in MATLAB. We’ll also provide some examples to help you understand the process. So if you’re ready to learn how to assign multiple variables at once in MATLAB, keep reading!

In MATLAB, you can assign multiple variables to the same value at once using the following syntax:

var1 = var2 = var3 = … = value

This is a very convenient way to assign the same value to multiple variables, and it can save you time and typing.

Syntax for assigning multiple variables at once

The syntax for assigning multiple variables at once in MATLAB is as follows:

Where `var1`, `var2`, `var3`, etc. are the variables to be assigned, and `value` is the value to be assigned to the variables.

For example, the following code assigns the value `10` to the variables `x`, `y`, and `z`:

x = y = z = 10;

Benefits of assigning multiple variables at once

There are several benefits to assigning multiple variables at once in MATLAB.

• It can save you time and typing. If you have multiple variables that you need to assign the same value to, you can do so with a single line of code instead of three.
• It can make your code more readable and easier to understand. When you assign multiple variables at once, it is clear that the variables are all being assigned the same value. This can help to prevent errors and make it easier to debug your code.
• It can be used to create arrays. When you assign multiple variables to the same value, you are essentially creating an array. This can be useful for storing data or performing calculations.

Examples of assigning multiple variables at once

The following are some examples of assigning multiple variables at once in MATLAB:

• To assign the value `10` to the variables `x`, `y`, and `z`, you would use the following code:
• To assign the values `1`, `2`, and `3` to the variables `a`, `b`, and `c`, you would use the following code:

a = b = c = [1, 2, 3];

• To assign the values of the vector `v` to the variables `x`, `y`, and `z`, you would use the following code:

x = y = z = v;

Assigning multiple variables at once in MATLAB can be a very convenient way to save time and typing, and it can also make your code more readable and easier to understand. There are many different ways to assign multiple variables at once, and the best way to do it will depend on your specific needs.

3. Limitations of assigning multiple variables at once

There are some limitations to assigning multiple variables at once in MATLAB.

• You cannot assign different values to the variables. For example, if you try to assign the value `10` to the variable `x` and the value `20` to the variable `y`, MATLAB will throw an error.
• You cannot assign variables of different types. For example, you cannot assign the value `10` to the variable `x`, which is a numeric variable, and the string `”Hello”` to the variable `y`, which is a character variable.

These limitations are in place to prevent errors and to ensure that your code is readable and understandable.

4. Examples of assigning multiple variables at once

d = e = f = {‘a’, ‘b’, ‘c’};

In the first example, we are assigning the value `10` to the three variables `x`, `y`, and `z`. In the second example, we are assigning the vector `[1, 2, 3]` to the three variables `a`, `b`, and `c`. In the third example, we are assigning the cell array `{‘a’, ‘b’, ‘c’}` to the three variables `d`, `e`, and `f`.

These are just a few examples of how you can assign multiple variables at once in MATLAB. For more information, please refer to the MATLAB documentation.

In this tutorial, you learned how to assign multiple variables at once in MATLAB. You learned about the limitations of assigning multiple variables at once, and you saw some examples of how you can use this technique in your own code.

I hope you found this tutorial helpful. Thank you for reading!

Q: How do I assign multiple variables at once in MATLAB?

A: There are a few ways to assign multiple variables at once in MATLAB.

• Using the comma operator: You can use the comma operator (,) to separate multiple variable names on the right-hand side of an assignment statement. For example, the following code will assign the values 1, 2, and 3 to the variables `a`, `b`, and `c`, respectively:

a, b, c = 1, 2, 3;

• Using the cell array: You can also use a cell array to assign multiple values to multiple variables. A cell array is a special type of array that can hold multiple data types, including strings, numbers, and other arrays. To create a cell array, you can use the `cell()` function. For example, the following code will create a cell array that contains the values 1, 2, and 3:

v = cell(3); v{1} = 1; v{2} = 2; v{3} = 3;

Once you have created a cell array, you can assign it to multiple variables using the `==` operator. For example, the following code will assign the values in the cell array `v` to the variables `a`, `b`, and `c`, respectively:

a = v{1}; b = v{2}; c = v{3};

• Using the `assign()` function: You can also use the `assign()` function to assign multiple values to multiple variables. The `assign()` function takes two arguments: the first argument is a cell array of variable names, and the second argument is a cell array of values. For example, the following code will assign the values in the cell array `v` to the variables `a`, `b`, and `c`, respectively:

assign({‘a’, ‘b’, ‘c’}, v);

Q: What are the advantages of assigning multiple variables at once?

A: There are a few advantages to assigning multiple variables at once.

• It can be more concise and efficient than assigning variables one at a time.
• It can reduce the chance of making a mistake when assigning variables.
• It can make your code more readable and easier to understand.

Q: Are there any disadvantages to assigning multiple variables at once?

A: There are no significant disadvantages to assigning multiple variables at once. However, you should be aware of the following potential issues:

• If you are not careful, you could accidentally assign the wrong value to a variable.
• If you are using a cell array to assign multiple values to multiple variables, you need to make sure that the cell array has the same number of elements as the number of variables you are assigning values to.

Q: What are some common mistakes people make when assigning multiple variables at once?

A: Some common mistakes people make when assigning multiple variables at once include:

• Accidentally assigning the wrong value to a variable.
• Forgetting to use the comma operator (,) to separate multiple variable names on the right-hand side of an assignment statement.
• Using a cell array with the wrong number of elements.

Q: How can I avoid making mistakes when assigning multiple variables at once?

A: To avoid making mistakes when assigning multiple variables at once, you can follow these tips:

• Be careful when typing in the values of the variables. Make sure that you are not accidentally typing in the wrong value.
• Use the comma operator (,) to separate multiple variable names on the right-hand side of an assignment statement. This will help you to avoid accidentally assigning the same value to multiple variables.

We hope that this blog post has been helpful. If you have any questions or comments, please feel free to leave them below.

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In MATLAB environment, every variable is an array or matrix.

You can assign variables in a simple way. For example,

MATLAB will execute the above statement and return the following result −

It creates a 1-by-1 matrix named x and stores the value 3 in its element. Let us check another example,

Please note that −

Once a variable is entered into the system, you can refer to it later.

Variables must have values before they are used.

When an expression returns a result that is not assigned to any variable, the system assigns it to a variable named ans, which can be used later.

For example,

You can use this variable ans −

Let's look at another example −

Multiple Assignments

You can have multiple assignments on the same line. For example,

I have forgotten the Variables!

The who command displays all the variable names you have used.

The whos command displays little more about the variables −

• Variables currently in memory
• Type of each variables
• Memory allocated to each variable
• Whether they are complex variables or not

The clear command deletes all (or the specified) variable(s) from the memory.

Long Assignments

Long assignments can be extended to another line by using an ellipses (...). For example,

The format Command

By default, MATLAB displays numbers with four decimal place values. This is known as short format .

However, if you want more precision, you need to use the format command.

The format long command displays 16 digits after decimal.

For example −

MATLAB will execute the above statement and return the following result−

Another example,

The format bank command rounds numbers to two decimal places. For example,

MATLAB displays large numbers using exponential notation.

The format short e command allows displaying in exponential form with four decimal places plus the exponent.

The format long e command allows displaying in exponential form with four decimal places plus the exponent. For example,

The format rat command gives the closest rational expression resulting from a calculation. For example,

Creating Vectors

A vector is a one-dimensional array of numbers. MATLAB allows creating two types of vectors −

• Row vectors
• Column vectors

Row vectors are created by enclosing the set of elements in square brackets, using space or comma to delimit the elements.

Column vectors are created by enclosing the set of elements in square brackets, using semicolon(;) to delimit the elements.

Creating Matrices

A matrix is a two-dimensional array of numbers.

In MATLAB, a matrix is created by entering each row as a sequence of space or comma separated elements, and end of a row is demarcated by a semicolon. For example, let us create a 3-by-3 matrix as −

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MATLAB – Variables

Prerequisite: Getting Started with MATLAB

A variable in simple terms is a storage place that has some memory allocated to it. Basically, a variable used to store some form of data. Different types of variables require different amounts of memory and have some specific set of operations that can be applied to them. The Matlab workspace store all the variables that you create or use during a session. 

Creating Variables

To create a variable enter the name of the variable in the command window, followed by an = operator, and then assign it some values .

Example: 

  Output:

  Note:  

• If you don’t put ‘;’ after the variable name, Matlab will display its content after hitting enter.
• If you don’t give any name to your variable by default Matlab name it with an answer.
• By default, Matlab treats all variables as matrices if you write just 1 it will store it as 1×1 matrix.

To display the content of the Matlab variable you just need to type the name of the variable, and it will show its content on Command-Line:

  Example:

Multiple Assignments of Variables

We can also define the multiple variables in a single line using “;” operator.

Who command

Who lists in alphabetical order the names of all variables in the currently active workspace. To use this command variables should be present in the active workspace and memory allocated to each variable is necessary.

Assigning Vectors to variables

A vector is a one-dimensional array of numbers. Matlab allows you two types of vector: 

• Column Vector.

Row Vectors are created by enclosing numbers in square brackets separating with either space or comma.

Column Vectors are created by enclosing numbers in square brackets, separating each number with ;(semicolon).

Assigning Matrices to variables

A Matrix is a two-dimensional array of numbers. In Matlab, matrices are created by enclosing numbers in a square bracket write each row of numbers with space or comma separate and after each row put a semicolon. The below code will create a 3×3 matrix:

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MATLAB Variables and Assignments

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29 Questions

What is the result of multiplying the transpose of an orthogonal matrix by itself.

An identity matrix

What is the type of matrix R in the QR decomposition A = QR?

Upper triangular matrix

What is the condition for the uniqueness of the QR decomposition of a matrix A?

A is a nonsingular matrix

What is the purpose of the Gram-Schmidt process in the QR decomposition?

To orthogonalize a set of vectors

What is the matrix Q in the QR decomposition of a matrix A?

An orthogonal matrix

What is the MATLAB command to initiate a matrix of zeros with 3 rows and 3 columns?

Q=zeros(3,3)

What happens when an expression returns a result that is not assigned to any variable?

The system assigns it to a variable named answer

What is the purpose of the 'who' command in MATLAB?

To display the names of all variables

What is the default display format for numbers in MATLAB?

Four decimal place values

What happens when you use the 'clear' command without specifying any variable in MATLAB?

It deletes all variables from the memory

How can you extend a long assignment to another line in MATLAB?

Using a new line with the continuation of the assignment

What is the purpose of the 'whos' command in MATLAB?

To display the names and sizes of all variables

What is the purpose of the loop variable 'i' in the Matlab code for Gauss Elimination?

To iterate through the columns of the matrix

What is the output of the Gauss Elimination method for the given system of equations?

What is the purpose of the command 'a(j,:) = a(j,:) - m*a(i,:)' in the gauss elimination matlab code.

To perform the row operations

What is the name of the process used in the Matlab code to orthogonalize the matrix?

Gram-Schmidt orthogonalization

What is the purpose of the command 'x(n) = A(n,n+1)/A(n,n)' in the Gauss Elimination Matlab code?

To solve for the variable x(n)

What is the purpose of the command 'summ = summ + A(i,j)*x(j,:)' in the Gauss Elimination Matlab code?

To solve for the variable x(i)

What is the purpose of the matrix P in the context of projection matrices and least squares?

To project a vector onto another vector

What is the result of the code P*u in the provided example?

A 2x100 matrix where each column is a vector projected onto the vector v

What is the interpretation of the relative residual in the output of the lsqr function?

The ratio of the norm of the residual vector to the norm of the right-hand side vector

What is the relationship between the vectors u and v in the provided example?

u is projected onto v

What is the purpose of the hold on command in the provided code?

To hold the current plot and add new data to it

What is the primary goal of finding the least square fit for a system of equations?

To minimize the sum of the squares of the errors

What is the name of the process used to find the point on a plane that is closest to a given point?

What is the purpose of computing the svd of a matrix.

To diagonalize the matrix

What is the correct order of steps to compute the SVD of a matrix A?

Find AAT, find eigenvalues, find eigenvectors, normalize them

What is the relationship between the singular values and eigenvalues of a matrix A?

σ1 = λ1 and σ2 = λ2

What is the purpose of normalizing the eigenvectors in the SVD process?

To make the eigenvectors orthonormal

Understand how to work with variables in MATLAB, including assigning values, using previous results, and multiple assignments on the same line. Learn how to use the 'answer' variable and more!

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Lamenting the lack of multiple assignment in MATLAB

I support scientific applications at The University of Manchester (see my LinkedIn profile if you’re interested in the details) and part of my job involves working on code written by researchers in a variety of languages.  When I say ‘variety’ I really mean it – MATLAB, Mathematica, Python, C, Fortran, Julia, Maple, Visual Basic and PowerShell are some languages I’ve worked with this month for instance.

Having to juggle the semantics of so many languages in my head sometimes leads to momentary confusion when working on someone’s program.  For example, I’ve been doing a lot of Python work recently but this morning I was hacking away on someone’s MATLAB code.  Buried deep within the program, it would have been very sensible to be able to do the equivalent of this:

That is, I want to be able to take the first column of the matrix a and broadcast it out to the variables x,y and z. The code I’m working on uses MUCH bigger matrices and this kind of assignment is occasionally useful since the variable names x,y,z have slightly more meaning than a(1,3), a(2,3), a(3,3).

The only concise way I’ve been able to do something like this using native MATLAB commands is to first convert to a cell. In MATLAB 2013a for instance:

This works but I think it looks ugly and introduces conversion overheads. The problem I had for a short time is that I subconsciously expected multiple assignment to ‘Just Work’ in MATLAB since the concept makes sense in several other languages I use regularly.

Mathematica :

I’ll admit that I don’t often need this construct in MATLAB but it would definitely be occasionally useful. I wonder what other opinions there are out there? Do you think multiple assignment is useful (in any language)?

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in “coding the matrix” coursera course which uses python. We used multiple assignments very extensively. In python 3 they have added “rest of them” feature. like a, b, *c = range(10) a = 0, b = 1, c = rest of them. or a, *b, c = range(10) a = 0, c = 9, b = rest of them

Agreed. The funny thing is that MATLAB functions do support multiple assignment; only MATLAB arrays do not.

Noo! Splitting multiple returned function values like that is nearly always wrong! If a function returns several things, its because they belong together, so it should be hard to break them apart! You can lose a lot of meaning and hence readability by breaking things up like this.

I avoid it!

Just a footnote: At least in GNU Octave, you have CoW (Copy on Write) which means no extra overhead if the value being copied isn’t modified. In other words, col1 = a(:,1); col2 = a(:,2); and so on costs ZERO if you don’t change col1,col2,…

can you do: >>A=rand(4,3); >>save temp.dat A /ascii >>type temp.dat >>load temp.dat >>temp results in a variable named “temp” assigned to the 4X3 matrix.

If you could manipulate the load argument to load only a column?

[x,y,z] = deal(a(:,1))

Is the closest thing to what you’d want in matlab. The deal function can be used to copy a single input to multiple outputs.

That doesn’t do what we want:

>> a=rand(3)

a = 0.8147 0.9134 0.2785 0.9058 0.6324 0.5469 0.1270 0.0975 0.9575

>> [x,y,z] = deal(a(:,1))

x = 0.8147 0.9058 0.1270

y = 0.8147 0.9058 0.1270

z = 0.8147 0.9058 0.1270

x,y,z have each got a copy of the first column!

Multiple assignment is very obscure operation, because of its internal inconsistency.

In your example: [x,y,z] = a(:,1) is a priori not known what is the expected result. There is plenty of possibilities: 1. x = a(1,1), y = a(2,1, z=a(3,1) 2. x = a(1:2,1), y=a(3,1), z = [] … etc

So, I think the MATLAB guys are right, that do not implement multiple assignment.

and yet Julia, Python and Mathematica seem to do it fine?

In Octave you could write:

>> a = rand(3); >> [x,y,z] = num2cell(a(:,1)){:}

Since MATLAB does not support directly indexing into a result, you’ll have to use a temporary variable to hold the result:

>> tmp = num2cell(a(:,1)); >> [x,y,z] = deal(tmp{:});

or use a hack to reduce it to a one-liner:

>> [x,y,z] = subsref(num2cell(a(:,1)), substruct(‘{}’,{‘:’}))

This request shows up quite often on Stack Overflow :) http://stackoverflow.com/questions/linked/2337126

Similarly, say you wanted to extract the columns into separate variables, you would write:

>> [x,y,z] = subsref(num2cell(a,1), substruct(‘{}’,{‘:’}))

in Octave simply as:

>> [x,y,z] = num2cell(a,1){:}

which is equivalent to: x=a(:,1); y=a(:,2); z=a(:,3);

David Ketcheson,

MATLAB functions are different from MATLAB indexing. Each output argument from a function consists of either an entire variable from that function’s workspace or an entire cell from the VARARGOUT cell array. The boundaries of what should and should not be included in each output are clear.

As ludolph’s example shows, things get a bit more complicated when you’re indexing into a variable. There isn’t necessarily such a clear boundary between what should be in each “output.” There’s also the question of what happens if you specify more (probably error) or fewer (more complicated) outputs than there are elements/rows/columns/pages/etc. in the result of the indexing expression.

a = magic(3); [x, y] = a(:, 1); % What should x and y be, since a(:, 1) has three elements?

Mike Croucher,

What do Python, Mathematica, and Julia do with their equivalents of the expression above? I can think of at least two or three possibilities.

Expanding that example just a bit, what should be the result of this code?

a = magic(4); [x, y] = a(:, [2 3]);

1) One option would be to error because the result of the indexing expression does not have exactly two elements.

2) A second (linear indexing inspired) option would be to store a(1, 2) in x and a(2, 2) in y.

3) A third option would be to store a(:, 2) in x and a(:, 3) in y, since the indexing expression has two columns and there are two outputs. This would be ambiguous if the indexing expression resulted in a 2-by-2 matrix; do we split by rows or columns? Do we need to modify the syntax used for indexing in MATLAB to determine how to split the result in this ambiguous case?

4) A fourth (DEAL-based) option would be to store a(:, [2 3]) in both x and y.

Finally, you could encapsulate the NUM2CELL-based approach into a function if you wanted:

function varargout = dealOut(A) varargout = num2cell(A);

For Mathematica example, didn’t you mean

{x,y,z}=a[[All,1]]

Yes, I did. Thanks for pointing it out. Now fixed.

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Multiple left-hand-side partial assignment in Matlab

Consider the following matrix:

I want to assign the second dimension 3 to variable n. What is the most efficient way?

Why are the following not working?

• variable-assignment
• matrix-indexing

• Seems like the most neat way is to use a temporary variable. stackoverflow.com/questions/3627107/… –  godblessfq Aug 15, 2013 at 23:04

This is probably the simplest, and works for a with any number of dimensions:

If a is guaranteed to have exactly 2 dimensions, you could also use

and if you don't need the first variable, in recent versions of Matlab you can write

As for the things you have tried:

[[],n]=size(a) does not work because [] is not a variable to which you can assign anything.

n= num2cell(size(a)){2} does not work because you can't directly index like that in Matlab. You would need a temporary variable: temp = num2cell(size(a)); n=temp{2} . Or dispose of num2cell and do: temp = size(a); n=temp(2) .

• 2 The first code is the correct one. Careful about the others, size will return the product of the remaining dimensions if you dont specify enough output variables; example: x = rand(5,4,3,2); [~,n] = size(x); ( n will be equal to 4*3*2) –  Amro Aug 16, 2013 at 0:09
• if you dont know the number of dimensions, another way is to do: [~,n,~] = size(x) this will work even if ndims(x)==2 . Of course size(x,2) is the still the preferred way. –  Amro Aug 16, 2013 at 12:09
• Also, ~ doesn't work for older versions of matlab. Specifically R2009a on my laptop, not sure about other revisions. –  JustinBlaber Aug 16, 2013 at 16:16

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