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Programming Articles
Page 1242 of 2547
How to standardized a column in an R data frame?
The standardization means converting a vector or column of an R data frame in a way such that the mean of the same becomes 0 and the standard deviation becomes 1, that is it should be converted to standard normal distribution. In R, it can be easily done with the help of scale function. Check out the below example to understand how it is done.ExampleConsider the below data frame:> set.seed(3665) > x1 x2 x3 x4 x5 x6 df dfOutputx1 x2 x3 x4 x5 x6 1 1.3958185 49.39843 128.5224 3 4.183664 2.33406246 2 1.0467979 48.90103 120.5796 7 3.526731 0.02043217 3 0.9190516 ...
Read MoreFlatten 2D Vector in C++
Suppose we have a 2D vector, we have to design and implement an iterator to flatten that 2d vector. There will be different methods as follows −next() − This will return the next element of the current elementhasNext() − This will check whether next element is present or notSo, if the input is like [[1, 2], [3], [4]] then if we call the functions as follows −iterator.next();iterator.next();iterator.next();iterator.hasNext();iterator.hasNext();iterator.next();iterator.hasNext();then the output will be [1, 2, 3, true, true, 4, false]To solve this, we will follow these steps −Define one 2D array vDefine initializer this will take one 2D array v, rowPointer := ...
Read MoreMeeting Rooms II in C++
Suppose there is an array of meeting time intervals. There are two times start and end times [[s1,e1],[s2,e2],...] and each pair satisfies the rule (si < ei), We have to find the minimum number of conference rooms required.So, if the input is like [[0, 30], [5, 10], [15, 20]], then the output will be 2.To solve this, we will follow these steps −define one priority queue pqsort the intervals arrayret := 0for initialize i := 0, when i < size of intervals, update (increase i by 1), do −while (not pq is empty and top element of pq
Read MoreFactor Combinations in C++
Suppose we have a number. The numbers can be regarded as a product of its factors. So, 8 = 2 x 2 x 2; = 2 x 4. We have to make one function that takes an integer n and return all possible combinations of its factors.So, if the input is like 12, then the output will be [[2, 6], [2, 2, 3], [3, 4]]To solve this, we will follow these steps −Define a function solve(), this will take n, target, start, define one list of lists called retif n is same as 1, then −return retif n is not ...
Read MoreHow to extract columns based on particular column values of an R data frame that matchna pattern?
The column values of an R data frame can be easily extracted by subsetting with single square brackets but if we want to extract the column values that match a pattern then we need to use grepl function inside single square brackets, this will help us to match the pattern of the values in the data frame columns.ExampleConsider the below data frame:> set.seed(271) > x1 x2 df1 df1Output x1 x2 1 A242 B71 2 A123 B71 3 A242 B81 4 A242 B87 5 A123 B71 6 A321 B71 7 A187 ...
Read MoreHow to remove rows based on blanks in a column from a data frame in R?
Sometimes data is incorrectly entered into systems and that is the reason we must be careful while doing data cleaning before proceeding to analysis. A data collector or the sampled unit might enter blank to an answer if he or she does not find an appropriate option for the question. This also happens if the questionnaire is not properly designed or blank is filled by mistake. Also, if we have categorical variable then a control category might be filled with blank or we may want to have a blank category to use a new one at later stage. Whatever the ...
Read MoreProgram to evaluate Postfix Notation in C++
Suppose we have postfix expression and we have to evaluate the value. Postfix expression is also known as Reverse polish notation. Here we have to use the stack data structure to solve the postfix expressions.So if the expression is “21+3*”, then the answer will be 9.Let us see the steps −for each character ch in the postfix expression, doif ch is an operator $\odot$ , thena := pop first element from stack, b := pop second element from the stackres := b $\odot$ apush res into the stackelse if ch is an operand, thenadd ch into the stackreturn element of ...
Read MoreGraph Valid Tree in C++
Suppose we have n nodes they are labeled from 0 to n-1 and a list of undirected edges [u, v], We have to define a function to check whether these edges make up a valid tree or not.So, if the input is like n = 5, and edges = [[0, 1], [0, 2], [0, 3], [1, 4]], then the output will be trueTo solve this, we will follow these steps −Define a function dfs(), this will take node, par, graph, and another array called visited, if visited[node] is same as 1, then −return trueif visited[node] is same as 2, then ...
Read MoreHow to create a data frame in R with list elements?
If a list has the same length of elements (not sub-elements) as the length of each vector for which we want to create the data frame then we first need to create the data frame of vectors then we can easily add the list into the data frame. But if we have a list and other vectors then data frame cannot be created as data.frame function will read each value of the list separately.Example> df1 df1Output x y 1 6 1 2 8 1 3 6 2 4 8 1 5 5 1 6 3 1 7 6 1 8 ...
Read MoreHow to reduce a matrix in R to echelon form?
The echelon form of a matrix is the matrix that has the following characteristics:1. The first non-zero element in each row, called the leading entry, is 1.2. Each leading entry is in a column to the right of the leading entry in the previous row.3. Rows with all zero elements, if any, are below rows having a non-zero element.In R, we can use echelon function of matlib package to find the echelon form of the matrix.Example> M MOutput [, 1] [, 2] [, 3] [, 4] [, 5] [1, ] 8 11 3 10 13 [2, ] 9 ...
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