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Articles by Nizamuddin Siddiqui
Page 95 of 196
How to find the cumulative sum for factor levels in an R data frame?
Cumulative sums are mostly used in descriptive analysis of data but sometimes we might want to calculate them in understanding the time series analysis for moving sums but it is very rare. If we have a factor column in an R data frame then it would not make sense to find the cumulative sum for all factor levels together, we must find the cumulative sums for each level. This can be easily done by using ave function.ExampleConsider the below data frame −set.seed(15) x1
Read MoreHow to create histogram with relative frequency in R?
The relative frequency histogram can be created for the column of an R data frame or a vector that contains discrete data. For this purpose, we can use PlotRelativeFrequency function of HistogramTools package along with hist function to generate histogram. For example, if we have a vector x for which we want to create a histogram with relative frequencies then it can be done as PlotRelativeFrequency(hist(x)).ExampleConsider the below vector −x
Read MoreHow to generate random samples rounded to 4 decimal places in R?
Random samples can be generated in many ways such as using discrete and continuous distributions, using integer vectors, using numerical vectors, using character vectors and/or factor vectors, also with columns of a data set. If we have the sample that is continuous in nature then the values are likely to contain many values after decimal point and we can limit those values to 4 or use any other limit using round function.Examplex1
Read MoreHow to generate a normal random vector using the mean of a vector in R?
To create a normal random vector, we can use rnorm function with mean and standard deviation as well as without passing these arguments. If we have a different vector derived from another distribution or simply represent some numbers then we can use the mean of that vector in the rnorm function for mean argument.Exampleset.seed(101) x1
Read MoreHow to join points in a point chart with lines using ggplot2 in R?
Usually, a point chart is created to assess the relationship or movement of two variables together but sometimes these points are scattered in a way that makes confusion. Hence, data analyst or researcher try to visualize this type of graph by joining the points with lines. In ggplot2, this joining can be done by using geom_line() function.Consider the below data frame −Exampleset.seed(111) x
Read MoreHow to find the index of the last occurrence of repeated values in a vector in R?
Indexing helps us to understand the location of the value in the vector. If we have a vector that contains repeated values then we might want to figure out the last occurrence of the repeated value. For example, if we have a vector x that contains 1, 1, 2, 1, 2 then the last occurrence of repeated values will be 4 and 5 because the last 1 is at 4th position and 2 is at the 5th position. We can find this by using tapply function in R.Examplex1
Read MoreHow to take a subset of a matrix in R with finite values only if the matrix contains NA and Inf values?
If we have a matrix that contains NA or Inf values and we want to take the subset of that matrix with finite values then only the rows that do not contain NA or Inf values will be the output. We can do this in R by using rowSums and is.finite function with negation operator !.Exampleset.seed(999) M1
Read MoreHow to find the maximum of factor levels in numerical column and return the output including other columns in the R data frame?
When we have factor column that helps to differentiate between numerical column then we might want to find the maximum value for each of the factor levels. This will help us to compare the factor levels in terms of their maximum and if we want to do this by getting all the columns in the data frame then aggregate function needs to be used with merge function.Consider the below data frame −Exampleset.seed(78) Group
Read MoreHow to find 95% confidence interval for binomial data in R?
The binomial data has two parameters, the sample size and the number of successes. To find the 95% confidence interval we just need to use prop.test function in R but we need to make sure that we put correct argument to FALSE so that the confidence interval will be calculated without continuity correction. In the below examples, we have found the 95% confidence interval for different values of sample size and number of successes.Exampleprop.test(x=25, n=100, conf.level=0.95, correct=FALSE)Output1-sample proportions test without continuity correction data: 25 out of 100, null probability 0.5 X-squared = 25, df = 1, p-value = 5.733e-07 alternative ...
Read MoreHow to extract correlation coefficient value from correlation test in R?
To perform the correlation test in R, we need to use cor.test function with two variables and it returns so many values such as test statistic value, degrees of freedom, the p-value, the confidence interval, and the correlation coefficient value. If we want to extract the correlation coefficient value from the correlation test output then estimate function could be used as shown in below examples.Examplex1
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