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2 maj 2012 · I have a large matrix, m, and am trying to count the number of a specific value (i.e. How many indexes are of the value 4?) I tried using val = sum(m == 4); but I end up with val being ...
- Find Array Elements That Meet Conditions - MATLAB & Simulink - MathWorks
Find Array Elements That Meet Conditions. This example shows...
- Find Array Elements That Meet Conditions - MATLAB & Simulink - MathWorks
Find Array Elements That Meet Conditions. This example shows how to filter the elements of an array by applying conditions to the array. For instance, you can examine the even elements in a matrix, find the location of all 0s in a multidimensional array, or replace NaN values in data.
To find array elements that meet a condition, use find in conjunction with a relational expression. For example, find(X<5) returns the linear indices to the elements in X that are less than 5. To directly find the elements in X that satisfy the condition X<5, use X(X<5).
As pointed out in a few other answers, you can iterate over all elements in a matrix A (of any dimension) using a linear index from 1 to numel(A) in a single for loop. There are also a couple of functions you can use: arrayfun and cellfun .
If you would like to create a matrix that counts by a unit other than one, add a second colon that denotes what numbers will be included. For example, >> [2:2:10;12:2:20]
There are a number of ways to create a matrix in Matlab. We begin by simply entering data directly. Entries on each row are separated by a space or comma and rows are separated by semicolons, (or newlines). We say that this matrix is of size 4-by-3 indicating that it has 4 rows and 3 columns.
MATLAB has many functions that help create matrices with certain values or a particular structure. For example, the zeros and ones functions create matrices of all zeros or all ones. The first and second arguments of these functions are the number of rows and number of columns of the matrix, respectively.
