Introduction to Matlab fit. MATLAB fit method can be used to fit a curve or a surface to a data set. Fitting a curve to data is a common technique used in Artificial intelligence and Machine learning models to predict the values of various attributes. 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. You can perform these tasks using a combination of the relational and logical operators. Run the command by entering it in the MATLAB. 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. You can perform these tasks using a combination of the relational and logical operators.
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. You can perform these tasks using a combination of the relational and logical operators. The relational operators (>, <, >=, <=, , ~=) impose conditions on the array, and you can apply multiple conditions by connecting them with the logical operators and, or, and not, respectively denoted by the symbols &, |, and ~.
In this published M-file, we will use MATLAB to solve problems about lines and planes in three-dimensional space. The mathematical content corresponds to chapter 11 of the text by Gulick and Ellis. We begin with the problem of finding the equation of a plane through three points. Example 1: Find an equation for the plane through the points (1.
Apply a Single Condition
To apply a single condition, start by creating a 5-by-5 matrix that contains random integers between 1 and 15. Reset the random number generator to the default state for reproducibility.
Use the relational less than operator, <, to determine which elements of A are less than 9. Store the result in B.
The result is a logical matrix. Each value in B represents a logical 1 (true) or logical 0 (false) state to indicate whether the corresponding element of A fulfills the condition A < 9. For example, A(1,1) is 13, so B(1,1) is logical 0 (false). However, A(1,2) is 2, so B(1,2) is logical 1 (true).
Although B contains information about which elements in A are less than 9, it doesn’t tell you what their values Mx player audio track hindi download. are. Rather than comparing the two matrices element by element, you can use B to index into A.
The result is a column vector of the elements in A that are less than 9. Since B is a logical matrix, this operation is called logical indexing. In this case, the logical array being used as an index is the same size as the other array, but this is not a requirement. For more information, see Array Indexing.
Some problems require information about the locations of the array elements that meet a condition rather than their actual values. In this example, you can use the find function to locate all of the elements in A less than 9.
The result is a column vector of linear indices. Each index describes the location of an element in A that is less than 9, so in practice A(I) returns the same result as A(B). The difference is that A(B) uses logical indexing, whereas A(I) uses linear indexing.
Apply Multiple Conditions
You can use the logical and, or, and not operators to apply any number of conditions to an array; the number of conditions is not limited to one or two.
First, use the logical and operator, denoted &, to specify two conditions: the elements must be less than 9 and greater than 2. Specify the conditions as a logical index to view the elements that satisfy both conditions.
The result is a list of the elements in A that satisfy both conditions. Be sure to specify each condition with a separate statement connected by a logical operator. For example, you cannot specify the conditions above by A(2<A<9), since it evaluates to A(2<A | A<9).
Next, find the elements in A that are less than 9 and even numbered.
The result is a list of all even elements in A that are less than 9. The use of the logical NOT operator, ~, converts the matrix mod(A,2) into a logical matrix, with a value of logical 1 (true) located where an element is evenly divisible by 2.
Finally, find the elements in A that are less than 9 and even numbered and not equal to 2.
Matlab Find Value In Matrix
The result, 8, is even, less than 9, and not equal to 2. It is the only element in A that satisfies all three conditions.
Use the find function to get the index of the element equal to 8 that satisfies the conditions.
The result indicates that A(14) = 8.
Replace Values That Meet a Condition
Sometimes it is useful to simultaneously change the values of several existing array elements. Use logical indexing with a simple assignment statement to replace the values in an array that meet a condition.
Replace all values in A that are greater than 10 with the number 10.
Next, replace all values in A that are not equal to 10 with a NaN value.
Lastly, replace all of the NaN values in A with zeros and apply the logical NOT operator, ~A.
The resulting matrix has values of logical 1 (true) in place of the NaN values, and logical 0 (false) in place of the 10s. The logical NOT operation, ~A, converts the numeric array into a logical array such that A&C returns a matrix of logical 0 (false) values and A|C returns a matrix of logical 1 (true) values.
See Also
and | find | isnan | Logical Operators: Short Circuit | nan | not | or | xor
| MATLAB Function Reference |
Find indices and values of nonzero elements
Syntax
Description
indices = find(X)returns the linear indices corresponding to the nonzero entries of the array X. If none are found, find returns an empty, 0-by-1 matrix. In general, find(X) regards X as X(:), which is the long column vector formed by concatenating the columns of X.
indices = find(X, k) or indices = find(X, k, 'first') returns at most the first k indices corresponding to the nonzero entries of X. k must be a positive integer, but it can be of any numeric data type.
indices = find(X, k, 'last') returns at most the last k indices corresponding to the nonzero entries of X.
[i,j] = find(..)returns the row and column indices of the nonzero entries in the matrix X. This syntax is especially useful when working with sparse matrices. If X is an N-dimensional array with N > 2, j contains linear indices for the dimensions of X other than the first.
Matlab Find Value In Array
[i,j,v] = find(..)returns a column vector v of the nonzero entries in X, as well as row and column indices.
Examples
returns linear indices for the nonzero entries of X.
You can use a logical expression to define X. For example,
returns linear indices corresponding to the entries of X that are greater than 2.
The following commands
return
a vector of row indices of the nonzero entries of X,
a vector of column indices of the nonzero entries of X, and
a vector containing the nonzero entries of X.
Some operations on a vector
For the matrix
returns the indices of the first four entries of M that are greater than 3.
If X is a vector of all zeros, find(X) returns an empty, 0-by-1 matrix. For example,
See Also
nonzeros, sparse, colon, logical operators (elementwise and short-circuit), relational operators, ind2sub
| filter2 | findall |
Matlab Find Index In Cell Array
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