Matlab size

length

Main Content

Description

example

returns the length of the largest array dimension in . For vectors, the length is simply the number of elements. For arrays with more dimensions, the length is . The length of an empty array is zero.

Examples

collapse all

Number of Vector Elements

Find the length of a uniformly spaced vector in the interval .

Length of Rectangular Matrix

Find the length of a 3-by-7 matrix of zeros.

X = zeros(3,7); L = length(X)

String Array

Create a string array and compute its length, which is the number of elements in each row.

X = ["a""b""c"; "d""e""f"]
X = 2x3 string "a" "b" "c" "d" "e" "f"

Length of Structure Fields

Create a structure with fields for and . Use the function to apply to each field.

S = struct('Day',[1 13 14 26],'Month',{{'Jan','Feb', 'Mar'}})
S = struct with fields: Day: [1 13 14 26] Month: {'Jan' 'Feb' 'Mar'}
L = structfun(@(field) length(field),S)

Input Arguments

collapse all

— Input array
scalar | vector | matrix | multidimensional array

Input array, specified as a scalar, vector, matrix, or multidimensional array.

Complex Number Support: Yes

Tips

  • To find the number of characters in a string or character vector, use the function.

  • does not operate on tables. To examine the dimensions of a table, use the , , or functions.

Extended Capabilities

Tall Arrays
Calculate with arrays that have more rows than fit in memory.

This function fully supports tall arrays. For more information, see Tall Arrays.

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

HDL Code Generation
Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

Thread-Based Environment
Run code in the background using MATLAB® or accelerate code with Parallel Computing Toolbox™ .

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

This function fully supports GPU arrays. For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Distributed Arrays
Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

This function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).

Introduced before R2006a

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MATLAB Function Reference   
size

Array dimensions

Syntax

  • d = size(X) [m,n] = size(X) m = size(Xdim) [d1,d2,d3,...,dn] = size(X)

Description

returns the sizes of each dimension of array in a vector with elements.

returns the size of matrix in separate variables and .

returns the size of the dimension of specified by scalar .

returns the sizes of the first dimensions of array in separate variables.

If the number of output arguments does not equal , then for:


returns ones in the "extra" variables, i.e., outputs through .

contains the product of the sizes of the remaining dimensions of i.e., dimensions through .
    Note    For a Java array, returns the length of the Java array as the number of rows. The number of columns is always 1. For a Java array of arrays, the result describes only the top level array.

Examples

Example 1. The size of the second dimension of is 3.

  • m = size(rand(2,3,4),2) m = 3

Here the size is output as a single vector.

  • d = size(rand(2,3,4)) d = 2 3 4

Here the size of each dimension is assigned to a separate variable.

  • [m,n,p] = size(rand(2,3,4)) m = 2 n = 3 p = 4

Example 2. If X = ones(3,4,5), then

  • [d1,d2,d3] = size(X) d1 = d2 = d3 = 3 4 5

But when the number of output variables is less than ndims(X):

  • [d1,d2] = size(X) d1 = d2 = 3 20

The "extra" dimensions are collapsed into a single product.

If n > ndims(X), the "extra" variables all represent singleton dimensions:

  • [d1,d2,d3,d4,d5,d6] = size(X) d1 = d2 = d3 = 3 4 5 d4 = d5 = d6 = 1 1 1

See Also

, ,


   sinh size (serial) 

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Size Function in MATLAB

Size Function in MATLAB

Introduction to Size Function in MATLAB

MATLAB provides us with plenty of functionalities, useful in various computational problems. In this article, we will study a powerful MATLAB function called ‘MATLAB size’. Before we understand how to calculate size of an array in MATLAB, let us first understand what exactly SIZE function does. Size function in MATLAB will return a row vector, whose elements will be the size of the respective dimensions of the array passed in the input.

Syntax of Size function in MATLAB:

Description of Size Function in MATLAB

  1. A = size(Y), this function will return the size of each dimension of the array passed as input.
  2. [a, b] = size(Y), this function will return the size of input matrix in 2 separate variables ‘a’ and ‘b’
  3. A = size(Y,dim), this function will return the size of Y’s dimension, specified by the input scalar dim.
  4. [dim1,dim2,dim3,…,dimN] = size(Y), this function will return the size of ‘n’ dimensions of input array X in separate variables.

In case the number of arguments ‘n’ in output are not equal to ndims(Y), then if:

n > ndims(Y)The function will return those present in the extra variable
n < ndims(Y)‘dn’ will contain the product of sizes of remaining dimensions of Y

Now let us understand the computation of size in MATLAB with various examples:

Examples to Implement Size Function in MATLAB

Below are the examples Size Function in MATLAB:

Example #1

Let us first define our input array as: rand(2, 4, 5)

As we can see in our input, the size of the third dimension in rand(2,4, 5) is 5.Let us try to find the same with the help of ‘size’ function.

  • To find out the size of third dimension, this is how our input will look like in MATLAB:

a = size(rand(2, 4, 5), 3)

Code:

Output:

Size Function in MATLAB 1

  • As we can see in the output, we have got the size of 3rd dimension, i.e, 5.

For the same input array, we can also get the size as one vector. Let us understand how we can achieve it:

a = size(rand(2, 4, 5))

This is how our input and output will look like in MATLAB console:

Code:

Output:

Size Function in MATLAB 1

  • As we can see in the output, we have got the size of all dimensions in single vector.

To assign sizes of dimensions to separate variables, we can use below code:

[a,b, c] = size(rand(2, 4, 5))
a = 2
b =4
c =5

This is how our input and output will look like in MATLAB console:

Code:

Output:

Size Function in MATLAB 1

As we can observe in the output, we have got size for all dimensions in separate variables.

Example #2

Let us first define a different input array.

A = ones(4, 3, 2)

Here, we are creating 2 arrays of size 4 x 3, with all ‘unity’ elements.

To get size of the dimension, below is our code:

[a, b, c] = size(A)

This is how our input and output will look like in MATLAB console:

Code:

Output:

Unity Elements Example 2

Example #3

Next, let us take the example when our output variables are less than ndims (Y). Here also, we will use the same array as in the above example

[a, b] = size(Y)

As we can see, the input has 3 size dimensions, but our output variables are only 2. In such cases, the last variable will be the product of all remaining dimensions.So, in our case, the product of last two dimensions is collapsed to last variable.

This is how our input and output will look like in MATLAB console:

Code:

Output:

Dimensions Example 3

As we can observe in the output, the last variable contains product of 3 and 2, which are size of last 2 dimensions.

Conclusion

So,in this article we learnt, size function can be used to calculate size of any array in MATLAB. Also, we can pass the number of arguments as per our requirement. MATLAB provides us with the product of size in case we pass less arguments than required.

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MATLAB Function ReferencePrevious page   Next Page
size

Array dimensions

Syntax

  • d = size(X) [m,n] = size(X) m = size(Xdim) [d1,d2,d3,...,dn] = size(X)

Description

returns the sizes of each dimension of array in a vector with elements. If is a scalar, which MATLAB regards as a 1-by-1 array, returns the vector .

returns the size of matrix in separate variables and .

returns the size of the dimension of specified by scalar .

for > 1, returns the sizes of the dimensions of the array in the variables d1,d2,d3,...,dn, provided the number of output arguments equals . If does not equal , the following exceptions hold:


equals the size of the th dimension of for , but equals the product of the sizes of the remaining dimensions of that is, dimensions through .


returns ones in the "extra" variables, that is, those corresponding to through .
    Note    For a Java array, returns the length of the Java array as the number of rows. The number of columns is always 1. For a Java array of arrays, the result describes only the top level array.

Examples

Example 1. The size of the second dimension of is 3.

  • m = size(rand(2,3,4),2) m = 3

Here the size is output as a single vector.

  • d = size(rand(2,3,4)) d = 2 3 4

Here the size of each dimension is assigned to a separate variable.

  • [m,n,p] = size(rand(2,3,4)) m = 2 n = 3 p = 4

Example 2. If X = ones(3,4,5), then

  • [d1,d2,d3] = size(X) d1 = d2 = d3 = 3 4 5

But when the number of output variables is less than ndims(X):

  • [d1,d2] = size(X) d1 = d2 = 3 20

The "extra" dimensions are collapsed into a single product.

If n > ndims(X), the "extra" variables all represent singleton dimensions:

  • [d1,d2,d3,d4,d5,d6] = size(X) d1 = d2 = d3 = 3 4 5 d4 = d5 = d6 = 1 1 1

See Also

, , ,


Previous page   sinh slice Next page

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Size matlab

size

Main Content

Description

example

returns a row vector whose elements are the lengths of the corresponding dimensions of . For example, if is a 3-by-4 matrix, then returns the vector .

If is a table or timetable, then returns a two-element row vector consisting of the number of rows and the number of table variables.

example

returns the length of dimension when is a positive integer scalar. Starting in R2019b, you can also specify as a vector of positive integers to query multiple dimension lengths at a time. For example, returns the lengths of the second and third dimensions of in the 1-by-2 row vector .

example

returns the lengths of the queried dimensions of separately.

Examples

collapse all

Size of 4-D Array

Create a random 4-D array and return its size.

A = rand(2,3,4,5); sz = size(A)

Query only the length of the second dimension of .

Starting in R2019b, you can query multiple dimension lengths at a time by specifying a vector dimension argument. For example, find the lengths of the first and third dimensions of .

Find the lengths of the second through fourth dimensions of .

Alternatively, you can list the queried dimensions as separate input arguments.

Size of Table

Create a table with 5 rows and 4 variables.

LastName = {'Smith';'Johnson';'Williams';'Jones';'Brown'}; Age = [38;43;38;40;49]; Height = [71;69;64;67;64]; Weight = [176;163;131;133;119]; BloodPressure = [124 93; 109 77; 125 83; 117 75; 122 80]; A = table(Age,Height,Weight,BloodPressure,'RowNames',LastName)
A=5×4 table Age Height Weight BloodPressure ___ ______ ______ _____________ Smith 38 71 176 124 93 Johnson 43 69 163 109 77 Williams 38 64 131 125 83 Jones 40 67 133 117 75 Brown 49 64 119 122 80

Find the size of the table. Although the variable contains two columns, only counts the number of variables.

Dimension Lengths as Separate Arguments

Create a random matrix and return the number of rows and columns separately.

A = rand(4,3); [numRows,numCols] = size(A)

Input Arguments

collapse all

— Input array
scalar | vector | matrix | multidimensional array

Input array, specified as a scalar, a vector, a matrix, or a multidimensional array.

Data Types: | | | | | | | | | | | | | | | | | | | | |

Complex Number Support: Yes

— Queried dimensions
positive integer scalar | vector of positive integer scalars

Queried dimensions, specified as a positive integer scalar or vector of positive integer scalars. If an element of is larger than , then returns in the corresponding element of the output.

Data Types: | | | | | | | | |

— List of queried dimensions
positive integer scalars

List of queried dimensions, specified as positive integer scalars separated by commas. If an element of the list is larger than , then returns in the corresponding element of the output.

Data Types: | | | | | | | | |

Output Arguments

collapse all

— Array size
row vector of nonnegative integers

Array size, returned as a row vector of nonnegative integers.

  • Each element of represents the length of the corresponding dimension of . If any element of is equal to , then is an empty array.

  • If is a scalar, then is the row vector .

  • If is a table or timetable, then is a two-element row vector containing the number of rows and the number of variables. Multiple columns within a single variable are not counted.

  • If is a character vector of type , then returns the row vector where is the number of characters. However, if is a string scalar, returns because it is a single element of a string array. For example, compare the output of for a character vector and string:

    To find the number of characters in a string, use the function.

Data Types:

— Dimension lengths
nonnegative integer scalar | vector of nonnegative integer scalars

Dimension lengths, returned as a nonnegative integer scalar when is a scalar and a row vector of nonnegative integer scalars when is a vector. If an element of the specified dimension argument is larger than , then returns in the corresponding element of .

Data Types:

— Dimension lengths listed separately
nonnegative integer scalars

Dimension lengths listed separately, returned as nonnegative integer scalars separated by commas.

  • When is not specified and fewer than output arguments are listed, then all remaining dimension lengths are collapsed into the last argument in the list. For example, if is a 3-D array with size , then returns and .

  • When is specified, the number of output arguments must equal the number of queried dimensions.

  • If you specify more than output arguments, then the extra trailing arguments are returned as .

Data Types:

Tips

  • To determine if an array is empty, a scalar, or a matrix, use the functions , , and . You can also determine the orientation of a vector with the and functions.

Extended Capabilities

Tall Arrays
Calculate with arrays that have more rows than fit in memory.

This function fully supports tall arrays. For more information, see Tall Arrays.

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

GPU Code Generation
Generate CUDA® code for NVIDIA® GPUs using GPU Coder™.

HDL Code Generation
Generate Verilog and VHDL code for FPGA and ASIC designs using HDL Coder™.

Thread-Based Environment
Run code in the background using MATLAB® or accelerate code with Parallel Computing Toolbox™ .

This function fully supports thread-based environments. For more information, see Run MATLAB Functions in Thread-Based Environment.

GPU Arrays
Accelerate code by running on a graphics processing unit (GPU) using Parallel Computing Toolbox™.

This function fully supports GPU arrays. For more information, see Run MATLAB Functions on a GPU (Parallel Computing Toolbox).

Distributed Arrays
Partition large arrays across the combined memory of your cluster using Parallel Computing Toolbox™.

This function fully supports distributed arrays. For more information, see Run MATLAB Functions with Distributed Arrays (Parallel Computing Toolbox).

Introduced before R2006a

You have a modified version of this example. Do you want to open this example with your edits?

You clicked a link that corresponds to this MATLAB command:

Run the command by entering it in the MATLAB Command Window. Web browsers do not support MATLAB commands.

Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select: .

Select web site

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Select the China site (in Chinese or English) for best site performance. Other MathWorks country sites are not optimized for visits from your location.

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