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Introduction to Matlab find value in array

The following article provides an outline for Matlab find value in array. In matlab a function is used to find indices values and values of nonzero elements in the array known as “find values in array.” The find values in the array will help find the elements or numbers present in the given array or not.

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A = find(Z)

A = find(Z,n)

How to find value in an array?

Matlab find values in array used for find indices and values of nonzero elements in the given array. To find values of nonzero elements in array, we need to take all elements in array and use proper syntax.

The steps for find values of nonzero value using find values in array:

Step 1: We need to collect all inputs in one set or in an array.

Step 2: Then, we use a find value in array with proper syntax to find the nonzero element values.

Examples of Matlab find value in array

Given below are the examples of Matlab find value in array:

Example #1

Let us see an example related to matlab find values in array, as we know find values in array is used for find indices and values of nonzero elements in the given array. So in this example, we take a number in the range of 1 to 30 with the difference of 2, and these elements take into a variable ‘F’ the numbers are 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27 and 29. Now we want to find a specific element in the array ‘F’ for that; we use a == operator. Now we use find values in array to find a specific element in the array ‘F.’ Now, we find that 13 and 12 are present in the array or not. For that we can use find values in array as “D1 = find(F==13)” And “D2 = find(F==12)”. This line will find whether a 13 number is present in the given array or not, and if the number is present in the array, the function returns the position of that number into the array. And the number is not present, then it displays a message as “Empty matrix.”

Code:

D2 = find(F==12)

Output:

After executing the above Matlab code 1st, we created array F. We found the 13 number at 7th place in the array F. However, the number 12 is not present into the array; hence matlab find values in array function returns empty.

Example #2

Let see one more example of matlab find values in array function. In this example, we create a matrix, and then we see how matlab finds values in array works. So first, we started with creating a 2–by–2 matrix that contains random integer numbers among 1 to 4. Next, we used the magic function to create a 2–by–2 matrix. Then we used matlab to find values in the array function. For example, Z= magic(2) returns a 2–by–2 matrix with random integers between 1 and 4. After that, we used the “A = find(Z)” syntax, which returns the values of nonzero elements in the array.

Code:

A = find(Z)

Output:

After executing the above code magic function, created a 2–by–2 matrix containing random integer numbers of 1 to 4. And after that, matlab find values in array function returns the all elements of matrix Z into the variable A.

Example #3

Code:

R1 = find(G== 1.2)

Output:

After executing the above matlab code, we created an array G of decimal numbers. We found the 1.2 number at the 5th position in the array G.

Conclusion

In this article, we saw the concept of Matlab find values in array. Basically, matlab finds values in array used for indicating values of an element into the array. Matlab find values in array plays an important role for finding a position of elements in the array. If there is no element in to the array, it returns empty.

Find The Number Of Prime Pairs In An Array Using C++

In this article, we will explain everything about finding the number of prime pairs in an array using C++. We have an array arr[] of integers, and we need to find all the possible prime pairs present in it. So here is the example for the problem −

Input : arr[ ] = { 1, 2, 3, 5, 7, 9 } Output : 6 From the given array, prime pairs are (2, 3), (2, 5), (2, 7), (3, 5), (3, 7), (5, 7) Input : arr[] = {1, 4, 5, 9, 11} Output : 1 Approaches to Find the Solution Brute Force Approach

Now we will discuss the most basic approach of all, i.e., the Brute Force approach, and try to find another approach as this approach is not very efficient.

Example using namespace std; void seiveOfEratosthenes(int *arr, bool *prime, int n, int MAX){ bool p[MAX+1]; memset(p, true, sizeof(p)); p[1] = false; p[0] = false; for(int i = 2; i * i <= MAX; i++){ if(p[i] == true){ for(int j = i*2; j <= MAX; j += i){ p[j] = false; } } } for(int i = 0; i < n; i++){ if(p[arr[i]] == true) prime[i] = true; } } int main(){ int arr[] = {1, 2, 3, 5, 7, 8, 9}; int n = sizeof(arr) / sizeof(arr[0]); int answer = 0; int MAX = INT_MIN; for(int i = 0; i < n; i++){ MAX = max(MAX, arr[i]); } bool prime[n]; memset(prime, false, sizeof(prime)); seiveOfEratosthenes(arr, prime, n, MAX); for(int i = 0; i < n-1; i++){ for(int j = i+1; j < n; j++){ if(prime[i] == true && prime[j] == true) answer++; } } cout << answer << "n"; return 0; } Output 6

In this approach, we are making a bool array that is going to tell us if any element is prime or not, and then we are going through all the possible pairs and checking if both numbers in the pair are prime or not. If prime, then increment the answer by one and go on.

But this approach is not very efficient as its time complexity is O(N*N), where N is the size of our array so, now we are going to make this approach faster.

Efficient Approach

In this approach, most of the code will be the same, but the crucial change is that instead of going through all the possible pairs, we are just going to calculate them using a formula.

Example using namespace std; void seiveOfEratosthenes(int *arr, bool *prime, int n, int MAX){ bool p[MAX+1]; memset(p, true, sizeof(p)); p[1] = false; p[0] = false; for(int i = 2; i * i <= MAX; i++){ if(p[i] == true){ for(int j = i*2; j <= MAX; j += i){ p[j] = false; } } } for(int i = 0; i < n; i++){ if(p[arr[i]] == true) prime[i] = true; } } int main(){ int arr[] = {1, 2, 3, 5, 7, 8, 9}; int n = sizeof(arr) / sizeof(arr[0]); int answer = 0; int MAX = INT_MIN; for(int i = 0; i < n; i++){ MAX = max(MAX, arr[i]); } bool prime[n]; memset(prime, false, sizeof(prime)); seiveOfEratosthenes(arr, prime, n, MAX); for(int i = 0; i < n; i++){ if(prime[i] == true) answer++; } answer = (answer * (answer - 1)) / 2; cout << answer << "n"; return 0; } Output 6

As you can see, most of the code is the same as the previous approach, but the crucial change that drastically decreased our complexity is the formula that we used, i.e., n(n-1)/2, which will calculate our number of prime pairs.

Explanation of the Above Code

In this code, we are using Sieve of Eratosthenes to mark all the prime numbers until the Max element that we have in the array. In another bool array, we are index-wise marking the elements if they are prime or not.

Finally, we are traversing through the whole array, finding the total number of primes present, and finding all the possible pairs using formula n*(n-1)/2. With this formula, our complexity is reduced to O(N), where N is the size of our array.

Conclusion

In this article, we solve a problem to find the Number of prime pairs present in an array in O(n) time complexity. We also learned the C++ program for this problem and the complete approach (Normal and efficient) by which we solved this problem. We can write the same program in other languages such as C, java, python, and other languages.

How To Find The Hyperbolic Arcsine Of A Given Value In Golang?

In this tutorial, we will learn how to find the Hyperbolic Arc Sine of a given value in the Golang programming Language. Golang language has many packages with predefined functions that the developer can use without writing the complete logic.

To perform the mathematical operations and logic we have a math package in Golang. We will use this package only to find the Hyperbolic Arc Sine of a given value. We will also see how to import the package and also how to call a function this package consists of by writing a Golang code.

Hyperbolic Arc Sine Definition

Hyperbolic Arc Sine is a function similar to trigonometry functions. Hyperbolic Arc Sine is equal to the analogs of the trigonometric function. The formula for Hyperbolic Arc sine is written below and the value of Hyperbolic Arc Sine is at different angles.

Syntax asinh(x) = ln(x + √x^2 + 1) Graph Value of Hyperbolic Arc Sine at different angles

asinh(0) = 0

asinh(30) = 4.094622224331

asinh(45) = 4.499933104264

asinh(60) = 4.787561179994

asinh(90) = 5.192987713659

Algorithm

Step 1 – Declaring the variable to store the value of the guardian and answer of float32 type.

Step 2 – Initializing the variable of a value.

Step 3– Call the function of Hyperbolic Arc sine and pass the value.

Step 4 – Printing the result.

Example

In this example, we will write a Golang program in which we will import a math package and call the Hyperbolic Arc sine function.

package main import ( "fmt" "math" ) func main() { var value, answer float64 fmt.Println("Program to find the Hyperbolic Arc sine of a given value in the Golang programming language using a math package.") value = 4.5 answer = math.Asinh(value) fmt.Println("The Hyperbolic Arc sine value with the value of", value, "is", answer) } Output Program to find the Hyperbolic Arc sine of a given value in the Golang programming language using a math package. The Hyperbolic Arc sine value with the value of 4.5 is 2.209347708615334 Algorithm

Step 1 – Declaring the variable to store the value of the guardian and answer of float32 type.

Step 2 – Initializing the variable of a value.

Step 3 – Call the function of Hyperbolic Arc sine defined by us and pass the value as a parameter

Step 4 – Printing the result.

Example

In this example, we will write a Golang program in which we will import a math package and call the Hyperbolic Arc sine function in a separate function and call that function main.

package main import ( "fmt" "math" ) func HyperbolicArcSine(angle float64) float64 { return math.Asinh(angle) } func main() { var value, answer float64 fmt.Println("Program to find the Hyperbolic Arc Sine of a given value in the Golang programming language using a separate function in the same program.") value = 1 answer = HyperbolicArcSine(value) fmt.Println("The Hyperbolic Arc Sine value with the value of", value, "is", answer) } Output Program to find the Hyperbolic Arc Sine of a given value in the Golang programming language using a separate function in the same program. The Hyperbolic Arc Sine value with the value of 1 is 0.8813735870195432 Conclusion

These are two ways to find the Hyperbolic Arc sine by using the function in the math package and passing the value as a parameter. The second approach will provide abstraction in the program. To learn more about Golang you can explore these tutorials.

C++ Program To Find The Hyperbolic Arcsine Of The Given Value

Hyperbolic functions, which are defined using the hyperbola rather than the circle, are comparable to normal trigonometric functions. It returns the ratio parameter in the hyperbolic sine function from the supplied radian angle. But to do the opposite, or to put it another way. If we want to calculate the angle from the hyperbolic-sine value, we require inverse hyperbolic trigonometric operations like the hyperbolic arcsine operation.

This lesson will demonstrate how to use the hyperbolic inverse-sine (asinh) function in C++ to calculate the angle using the hyperbolic sine value, in radians. The hyperbolic inverse-sine operation follows the following formula −

$$mathrm{sinh^{-1}x:=:In(x:+:sqrt{x^2:+:1})},where :In: is: natural: logarithm:(log_e : k)$$

The asinh() function

From the hyperbolic sine value, the angle can be calculated using asinh() function. This function comes with the C++ standard library. We must import the cmath library before using this function. This method returns the angle in radians and takes a sine value as an argument. The following uses the simple syntax −

Syntax Algorithm

Take hyperbolic sine value x as input

Use asinh( x ) to calculate the sinh−1(x)

Return result.

Example

using

namespace

std

;

float

solve

(

float

)

{

float

answer

;

answer

asinh

(

)

;

return

answer

;

}

int

main

(

)

{

float

angle

ang_deg

;

angle

solve

(

2.3013

)

;

ang_deg

angle

180

3.14159

;

cout

“The angle (in radian) for given hyperbolic sine value 2.3013 is: “

angle

” = “

ang_deg

” (in degrees)”

endl

;

angle

solve

(

11.5487

)

;

ang_deg

angle

180

3.14159

;

cout

“The angle (in radian) for given hyperbolic sine value 11.5487 is: “

angle

” = “

ang_deg

” (in degrees)”

endl

;

angle

solve

(

0.86867

)

;

ang_deg

angle

180

3.14159

;

cout

“The angle (in radian) for given hyperbolic sine value 0.86867 is: “

angle

” = “

ang_deg

” (in degrees)”

endl

;

angle

solve

(

–

0.86867

)

;

ang_deg

angle

180

3.14159

;

cout

“The angle (in radian) for given hyperbolic sine value – 0.86867 is: “

angle

” = “

ang_deg

” (in degrees)”

endl

;

}

Output The angle (in radian) for given hyperbolic sine value 2.3013 is: 1.5708 = 90.0001 (in degrees) The angle (in radian) for given hyperbolic sine value 11.5487 is: 3.14159 = 180 (in degrees) The angle (in radian) for given hyperbolic sine value 0.86867 is: 0.785397 = 45 (in degrees) The angle (in radian) for given hyperbolic sine value - 0.86867 is: -0.785397 = -45 (in degrees)

The asinh() method, which receives the hyperbolic sine value in this case, returns the angle in radian format. We converted this output from radians to degrees using the formula below.

$$mathrm{theta_{deg}:=:theta_{rad}:timesfrac{180}{pi}}$$

Conclusion

To conduct the inverse hyperbolic operation using the sine value, we utilize the asinh() function from the cmath package. After receiving the value of the hyperbolic sine as input, this function outputs the desired angle in radians. In older versions of C and C++, the return type was double; later versions of C++ additionally used the overloaded form for float and long-double. The asinh() function will be invoked after casting the input parameter into the double type when an integer value is passed as an argument.

From Json Object To An Array In Javascript

The JSON (JavaScript object notation) Object can be created with JavaScript. JSON Object is always surrounded inside the curly brackets {}. The keys must be in strings and values must be in valid JSON data type. The data types like string, number, object, Boolean, array, and Null will be supported by JSON. The keys and values are separated by a colon(“:”) and a comma separates each key and value pair.

Syntax

Following is the syntax of JSON Object −

var JSONObj = {};

The below example is the basic declaration of a JSON object in JavaScript −

var JSONObj = { "Movie ":"Avatar", "Director":"James Cameron", "Budget_in_dollars": 250 };

An Array is a collection of similar data elements which will be stored at contiguous memory locations. Array elements can be accessed by using index numbers. These index numbers will start from 0.

Syntax

Following is the syntax to create an array −

const array = [element1, element2, ...];

Here is the basic declaration of the array in JavaScript −

const array = ["shirt","pant","shoe"]; Input-output scenario

Consider we have a JSON Object with values and key pairs and we need to convert the object to an array. It will be as shown in the below example when we try to convert the JSON Object to an array.

JSONObject = { "Fisrtname": 'Mohammed", "Lastname": "Ali" }; Output = [["Firstname", "Mohammed"], ["Lastname", "Ali"]] Object.keys()

The Object.keys() method in JavaScript will return an array with elements, these elements will be taken from the object’s enumerable properties. The ordering of the elements in the strings will be as same as in the object.

Let’s consider the example below, we have declared a JSON Object with key-value pairs. By using Object.keys() we have converted the object’s enumerable properties into an array as strings.

Example

Following is an example to convert a JSON object to an array using the object.keys() method −

const

JSON_obj

{

“Name”

“Ali”

“Hometown”

“Hyderabad”

“age”

“29”

}

;

var

array

Object

keys

(

JSON_obj

)

;

document

getElementById

(

“para”

)

innerHTML

array

;

Converting JSON Object into array by using for…in loop

We can convert the JSON Object to an array by using the for…in loop. This loop will iterate all the object’s enumerable properties which are string encoded. By default, the internal enumerable value is true, as we assigned the properties of the object via simple assignment.

Let’s consider an example, here we are creating a JSON Object and converting it into an array by pushing all its properties into an array. Here the loop will iterate the object together with keys and values and then they will be pushed into the array.

Example

Following is an example to convert a JSON object to an array using the for…in loop −

const

JSONobject

{

“name”

“yuvraj”

“role”

“batsmen”

“age”

“37”

“bat”

“left”

}

;

function

func

(

)

{

const

res_array

[

]

;

for

(

let

JSONobject

)

{

res_array

push

(

[

JSONobject

[

]

)

;

}

;

document

getElementById

(

“para”

)

innerHTML

res_array

;

}

;

Using Object.entries() method

The Object.entries() method in JavaScript will return an array containing the enumerable properties [key, value pairs] in the JSON Object.

By default, the internal enumerable value is true, as we assigned the properties of the object using a simple assignment, the ordering of properties in the array will be as same as in the object.

Example

In the example below, we have created a JSON Object, and using Object.entries() we have pushed both keys and values of the object into the empty array (res_array).

const

JSONobject

{

‘Movie’

‘RRR’

‘Actor1’

‘Ram Charan’

‘Actor2’

‘NTR’

‘Director’

‘SS Rajamouli’

}

;

function

func

(

)

{

const

resArray

[

]

;

for

(

const

[

key

value

]

Object

entries

(

JSONobject

)

{

resArray

push

(

[

key

}

value

}

]

)

;

}

document

getElementById

(

“heading1”

)

innerHTML

resArray

;

}

;

Working And Examples Of Matlab Textscan()

Introduction to Matlab Textscan

Inbuilt function from MATLAB, textscan() perform the operation of reading formatted data from text file or string, converting and writing data to cell array.Textscan() supports initializing reading from any point in a file. Once the user opens the file, textscan() can start reading from any point instructed by the user. The subsequent textscan() continues reading operation the file when the last textscan() operation is left off.

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Syntax

Syntax Description

C = textscan(fileID,formatSpec) This form of the command textscan() is used to read data from an open text file indicated by fileID into a cell array, C.

C = textscan(fileID,formatSpec,N) This form of the command textscan() is used to read data from an open text file indicated by fileID into a cell array, Cfor theformatSpec, N times. In order to read additional,textscan() can be called using the original fileIDagain.

C = textscan(chr,formatSpec) This form of the command textscan() is used to read data from the character vector ‘chr’ and store it in the cell array ‘C.’ While reading data from character vector, each time, recurring calls to textscan()re-initiate the scan from the beginning. A scan can be resumed from the last position on request for a position output.

Textscan()tries to match the data in ‘chr’ to the format given in the form offormatSpec.

C = textscan(chr,formatSpec,f) This form of the command textscan() is used to read dataforformatSpecf times, where f is a positive integer.

This form of the command textscan() is used to read data specifying options in the form of one or more Name, Value pair arguments.

The return value

For a file- value equals to return value of ftell(fileID)

Examples of Matlab Textscan

Different examples are mentioned below:

Example #1

Code:

chr_str = '0.31 3.24 5.67 6.44 9.17';Scan_str = textscan(chr_str,'%f'); celldisp(Scan_str)

Output:

Example #2

Code:

C_data0 = textscan(ID_file,’%d %f %f %f’)

Output:

Example #3

Code:

chr_str = 'It is;my code';Scan_str = textscan(chr_str,'%s','Delimiter',';','EmptyValue',-Inf); celldisp(Scan_str)

Output:

Working of TextScan()

Textscan()is designed to convert numeric fields to a specific output type, following MATLAB rules with respect to the process of overflow, truncation, and the application of NaN, Inf, and -Inf.

For example, the integer NaNis represented as zero in MATLAB. Therefore, if textscan() encounters an empty field associated with an integer format specifier, it returns the empty value as zero and not NaN.

Resuming a Text Scan

If textscan() fails to convert a data field, it does not proceed with the operation reading and returns the fields read before the failure. When reading from a file, the reading operation from the same file can be resumed by calling textscan() again having the same file identifier, filed, as the first input argument. For a string reading operation carried out by the textscan() method, the syntax of the two-output argument enables the user to resume the reading operation from the string at the point where the last reading operation is terminated. The following code talks about the implementation of this operation.

celldisp(lastpart)

Output:

Thetextscan() and textread() Functions exhibit similar functionalities, but they differ from each other in various aspects such as:

The textscan() function ensures better performance than that oftextread() method. Hence it is a better choice in case of reading large files.

With the textscan() function, the reading operation can be started reading from any point in the file. Once the file is open by the user as it is a prerequisite for textscan() that it requires the user to open the file first, then the user can have access to any position in the file to begin the textscan() at the desired point whereas the textread() function has limited feature of supporting reading operation only from the beginning of any file.

Subsequent textscan() operations start reading of the given file at that point where the earliertextscan() operation is left off. But in the case of the textread() function, it always begins from the beginning of the input file irrespective of the status of the reading operation carried out by any of the prior textread() function call.

Textscan()supports more options on the conversion of the data being read.

Textscan()is equipped with more user-configurable options that that of textread() operation.

Additional Note

Example:

3.7-2.1i

Output:

Example:

-4j

Output:

3. It is not recommended to include embedded white space to a complex number. Textscan() understands an embedded white space as a field delimiter.