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Page 1273 of 2109
How to find standard deviations for all columns of an R data frame?
To find the means of all columns in an R data frame, we can simply use colMeans function and it returns the mean. But for standard deviations, we do not have any direct function that can be used; therefore, we can use sd with apply and reference the columns to find the standard deviations for all column of an R data frame. For example, if we have a data frame df then the syntax using apply function to find the standard deviations for all columns will be apply(df, 2, sd), here 2 refers to the columns. If we want to ...
Read MoreHow to find the number of columns of an R data frame that satisfies a condition based on row values?
Sometimes we want to extract the count from the data frame and that count could be the number of columns that have same characteristics based on row values. For example, if we have a data frame containing three columns with fifty rows and the values are integers between 1 and 100 then we might want to find the number of columns that have value greater than 20 for each of the rows. This can be done by using rowSums function.ExampleConsider the below data frame −> x1 x2 x3 df dfOutput x1 x2 x3 1 9 72 9 2 5 20 6 ...
Read MoreHow to find the difference of values of each row from previous by group in an R data frame?
In Data Analysis, sometimes we need to find the difference of the current value from the previous value and it can be also needed for groups. It helps us to compare the differences among the values. In R, we can use dplyr package’s group_by and mutate function with lag.ExampleConsider the below data frame −> Group Frequency df1 df1Output Group Frequency 1 A 7 2 A 6 3 A 9 4 A 12 5 B 19 6 B 19 7 B 4 8 B 6 9 C 14 10 C 6 11 ...
Read MoreMaximum product of an increasing subsequence in C++
In this tutorial, we will be discussing a program to find maximum product of an increasing subsequence.For this we will be provided with an array of integers. Our task is to find the maximum product of any subsequence of the array with any number of elements.Example#include #define ll long long int using namespace std; //returning maximum product ll lis(ll arr[], ll n) { ll mpis[n]; //initiating values for (int i = 0; i < n; i++) mpis[i] = arr[i]; for (int i = 1; i < n; i++) for ...
Read MoreMaximum product of indexes of next greater on left and right in C++
In this tutorial, we will be discussing a program to find maximum product of indexes of next greater on left and right.For this we will be provided with an array of integers. Our task is to find the element with maximum Left-Right product (L(i)*R(i) where L(i) is closest index on left side and greater than current element and R(i) is closest index on right side and greater than current element).Example#include using namespace std; #define MAX 1000 //finding greater element on left side vector nextGreaterInLeft(int a[], int n) { vector left_index(MAX, 0); stack s; for (int i ...
Read MoreHow to add a new column to an R data frame with largest value in each row?
When we have a data frame that contains all numerical columns then we might want to find the largest value in each row. For example, if we have a sales data set in which each row represents a customer and columns represent the products with quantities of values as values then we might want to find the maximum of each row to find out who buys which product the most. This can be done by using max with apply function for rows.ExampleConsider the below data frame −> x1 x2 x3 x4 x5 df1 df1Output x1 ...
Read MoreHow to concatenate column values and create a new column in an R data frame?
Sometimes we want to combine column values of two columns to create a new column. This is mostly used when we have a unique column that maybe combined with a numerical or any other type of column. Also, we can do this by separating the column values that is going to be created with difference characters. And it can be done with the help of apply function.ExampleConsider the below data frame −> ID Country df1 df1Output ID Country 1 1 UK 2 2 UK 3 3 India 4 4 USA 5 5 USA 6 6 UK 7 7 Nepal 8 8 ...
Read MoreMaximum sum of increasing order elements from n arrays in C++
In this tutorial, we will be discussing a program to find maximum sum of increasing order elements from n arrays.For this we will be provided with N arrays of M size. Our task is to find the maximum sum by selecting one element from each array such that element from the previous array is smaller than the next one.Example#include #define M 4 using namespace std; //calculating maximum sum by selecting //one element int maximumSum(int a[][M], int n) { for (int i = 0; i < n; i++) sort(a[i], a[i] + M); int sum = ...
Read MoreHow to concatenate numerical vectors and a string to return a string in R?
In general, the concatenation of numerical vectors and string results in a vector of strings in R. For example, if we want to concatenate 1, 2, 3 with Tutorialspoint using paste function then it will result in a vector as: "Tutorialspoint 1" "Tutorialspoint 2" "Tutorialspoint 3". But if we want it to return as "Tutorialspoint 1 2 3" then we need to use collapse argument with paste function.Example1> x1Output[1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J"> y1Output[1] 1 9 6 3 8 1 8 5 9 1 2 8 3 8 4 5 10 1 6 3 ...
Read MoreHow to multiply each element of a numerical vector in R?
Sometimes we want to determine the multiplication of all the elements of a vector just like the sum. This might be required to test the changes in the mathematical operations that can be applied to a numerical vector. In base R, we have prod function which works same as sum but give us the multiplication of all the elements of a vector.Example> v1 v1Output[1] 1 2 3 4 5> prod(v1)Output[1] 120 Example> v2 v2Output[1] -0.500466629 0.394771317 0.575743107 0.026982141 0.812697502 [6] 0.995708241 2.198243938 -0.008609976 -0.931337300 -0.073743225> prod(v2)Output[1] 3.228448e-06Example> v3 v3Output[1] 1.7328245888 -0.5772304935 2.5161349689 3.0401656274 0.1669773313 [6] -0.0001252235 0.7649984733 2.4901543043 1.5618729422 2.4392364199> ...
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