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Articles on Trending Technologies
Technical articles with clear explanations and examples
Find speed of man from speed of stream and ratio of time with up and down streams in C++
In this problem, we are given two values S and N denoting the speed of stream in Km/h and ratio of time with up and down streams. Our task is to Find speed of man from the speed of stream and ratio of time with up and down streams.Let’s take an example to understand the problem, InputS = 5, N = 2Output15Solution ApproachA simple solution to the problem is by using the mathematical formula for the rowing problems. So, let’s see how the formula will work −speed of man = x km/h speed of stream = S km/h speed of ...
Read MoreHow to check if a data frame column contains duplicate values in R?
To check if a data frame column contains duplicate values, we can use duplicated function along with any. For example, if we have a data frame called df that contains a column ID then we can check whether ID contains duplicate values or not by using the command −any(duplicated(df$ID))Example1Consider the below data frame −ID
Read MoreHow to sort each row of an R data frame in increasing order?
To sort each row of an R data frame in increasing order, we can use apply function for sorting the columns and then transpose the output. For example, if we have a data frame called df that contains 5 columns then each row of df can be sorted in increasing order by using the command t(apply(df,1,sort)).Example1Consider the below data frame −x1
Read MoreHow to minus one column from another in an R matrix?
To minus one column from another in an R matrix, we first need to read the matrix as a data frame using as.data.frame then find minus the columns using minus sign and accessing the column of the data frame. To understand how it can be done look at the steps in below examples.ExampleConsider the below data frame −M1
Read MoreFind maximum sum taking every Kth element in the array in C++
In this problem, we are given an array arr[] and an integer k. Our task is to Find the maximum sum taking every Kth element in the array.Problem description: We need to find the maximum sum of the elements of the array such that they are k indexes apart. i.e. we need to maximize the sum, sum = arr[i] + arr[i+k] + arr[i + 2*k] + …. arr[i + p*k], such that (i + p*k) < nLet’s take an example to understand the problem, Inputarr[] = {5, 3, −1, 2, 4, −5, 6}, k = 4Output9ExplanationAll sums of every kth ...
Read MoreHow to convert negative values in a matrix to 0 in R?
To convert negative values in a matrix to 0, we can use pmax function. For example, if we have a matrix called M that contains some negative and some positive and zero values then the negative values in M can be converted to 0 by using the command pmax(M,0).ExampleConsider the below data frame −M1
Read MoreFind Maximum value of abs(i – j) * min(arr[i], arr[j]) in an array arr[] in C++
In this problem, we are given an array arr[] insisting of N integer values.Our task is to Find Maximum value of abs(i – j) * min(arr[i], arr[j]) in an array arr[].Problem description − we need to find the maximum product value of the minimum value of two elements and the absolute differences between their indexes. i.e. for two values i and j, we need to maximise, abs(i - j) * min(arr[i] , arr[j]).Inputarr[] = {5, 7, 3, 6, 4}Output16ExplanationThe maximum value is 16, between index 0 and 4 => abs(0 - 4)*min(arr[0], arr[4]) => 4*min(5, 4) => 4*4 = 16Solution ...
Read MoreHow to change the legend title in ggplot2 in R?
In ggplot2, by default the legend title is the title of the grouping column of the data frame. If we want to change that title then scale_color_discrete function. For example, if we have a data frame called df that contains two numerical columns x and y and one grouping column say group then the scatterplot with a different legend title can be created by using the below command −ggplot(df, aes(x, y, color=group))+geom_point()+scale_color_discrete("Gender")ExampleConsider the below data frame −> x y grp df dfOutput x y grp 1 -2.27846496 0.8121008 Male ...
Read MoreFind mean of subarray means in a given array in C++
In this problem, we are given an array arr[] of size n and an integer m. Our task is to Find mean of subarray means in a given array.Code Description − Here, we need to find the mean of array as the mean of means of subarray of size m.Let’s take an example to understand the problem, Inputarr[] = {2, 5, 3, 6, 1}, m = 3Output3.78ExplanationAll subarrays of size m are {2, 5, 3}, {5, 3, 6}, {3, 6, 1} Means of means of subarray of size m, $$(\left(\frac{2+5+3}{3}\right)+\left(\frac{5+3+6}{3}\right)+\left(\frac{3+6+1}{3}\right))/3=\left(\frac{10}{3}\right)+\left(\frac{14}{3}\right)+\left(\frac{10}{3}\right)/3=34/3/3=3.78$$Solution ApproachA simple solution to the problem is by finding all ...
Read MoreHow to find the row sum for each column by row name in an R matrix?
To find the row sum for each column by row name, we can use rowsum function. For example, if we have a matrix called M then the row sums for each column with row names can be calculated by using the command rowsum(M, row.names(M)).Example1> M1 rownames(M1) colnames(M1) M1Output V1 V2 Male 3 6 Female 6 5 Female 7 3 Female 2 5 Female 5 3 Female 4 4 Female 1 4 Female 4 4 Female 7 5 Male 2 5 Female 5 5 Male 7 1 Female 5 6 Male 6 5 Female 3 ...
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