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Articles by Nizamuddin Siddiqui
Page 174 of 196
How to represent the mean with vertical line in a histogram created by hist function in R?
The value of mean is an important characteristic of the data to be represented by a histogram, therefore, one might want to plot it with the histogram. If the histogram is created by using hist function then we can create a vertical line on the histogram with the help of abline function by defining mean of the data for vertical argument v.Exampleset.seed(101) x
Read MoreHow to represent the legend in a plot created by using plot function with colored straight lines or stars in R?
A legend helps us to differentiate between the type of values or any another division of values in a data set. These legends can be represented in many ways and two of these ways are straight lines and stars. To represent the legend in a plot created by using plot function with colored straight lines or stars, we need to correct lty and pch arguments.ExampleConsider the below vectors −set.seed(199) x
Read MoreHow to create a frequency polygon in R?
Frequency polygons are the graphs of the values to understand the shape of the distribution of the values. They are useful in comparing different data sets and visualising cumulative frequency distribution of the data sets. In base R, we can use polygon function to create the frequency polygon but first we should create a line plot for the two variables under consideration.ExampleConsider the below vectors x and y −set.seed(999) x
Read MoreHow to reduce the size of the area covered by legend in R for a plot created by using plot function?
By default, the area covered by legends for a plot created by using plot function is of full size that is 1 (the area size has a range of 0 to 1, where 1 refers to the full size and 0 refers to none). To reduce the size, we can use cex argument with the legend function as shown in the below example.ExampleConsider the below vectors and the plot created between these two vectors −x
Read MoreHow to create a standard normal distribution curve with 3-sigma limits in R?
A standard normal distribution has mean equals to zero and the standard deviation equals to one. Therefore, when we plot it with three sigma limits, we have six points on the X-axis referring to the plus and minus around zero. If the limits are defined then the plotting can be shown with larger width and that will change the display of the curve. We can do this by creating a sequence for the length of the standard normal variable and its density.Consider the below vectors corresponding to the limits and density−x
Read MoreHow to create bars with gap among them if there are more categories using ggplot2 in R?
When the number of categories is large in numbers for a variable and we want to create a bar plot then the display of the bar plot becomes a little ambiguous because the bars are plotted very close to each other. To make the bars clearly visible, we can reduce the width of the bars and set different colors for them to make them visually attractive.geom_bar(width=0.2,color="red")Consider the below data frame −x
Read MoreHow to create random sample based on group columns of a data.table in R?
Random sampling helps us to reduce the biasedness in the analysis. If we have data in groups then we might want to find a random sample based on groups. For example, if we have a data frame with a group variable and each group contains ten values then we might want to create a random sample where we will have two values randomly selected from each group. This can be done by using sample function inside .SDExampleConsider the below data.table −library(data.table) Group
Read MoreHow to extract values from an R data frame column that do not start and end with certain characters?
Sometimes we just want to extract the values of a data column based on initial and ending values of a column that has strings or sometimes the values of a column that has strings are recorded with some extra characters and we want to extract those values. For this purpose, we can use negation of grepl with single square brackets.ExampleConsider the below data frame −> x2 df2 head(df2, 20)Outputx2 1 Alabama 2 Alaska 3 American Samoa 4 Arizona 5 Arkansas 6 California 7 Colorado 8 Connecticut 9 Delaware 10 District of Columbia 11 Florida 12 Georgia 13 Guam 14 Hawaii ...
Read MoreHow to extract strings based on first character from a vector of strings in R?
Sometimes a vector strings have patterns and sometimes we need to make patterns from a vector of strings based on the characters. For example, we might want to extract the states name of United States of America from a vector that contains all the names. This can be done by using grepl function.ExampleConsider the below vector containing states name in USA −> US_states US_states[grepl("^A", US_states)] [1] "Alabama" "Alaska" "American Samoa" "Arizona" [5] "Arkansas" > US_states[grepl("^B", US_states)] character(0) > US_states[grepl("^C", US_states)] [1] "California" "Colorado" "Connecticut" > US_states[grepl("^D", US_states)] [1] "Delaware" "District of Columbia" > US_states[grepl("^E", US_states)] character(0) > US_states[grepl("^F", US_states)] [1] ...
Read MoreHow to find the n number of largest values in an R vector?
A vector may have thousands of values and each of them could be different or same also. It is also possible that values can be grouped or randomly selected but having few similar values. Irrespective of the values in a vector, to find some largest values we need to sort the vector in ascending order then the largest values will be selected.Examples> x1 x1 [1] -1.4447473195 3.2906645299 -0.4680055849 0.1611487482 -0.7715094280 [6] 0.4442103640 0.3702444686 0.0783124252 1.3476432299 1.0140576107 [11] -0.0968917066 0.4628821017 0.3102594626 -0.2946001275 0.1498108166 [16] -0.6002154305 0.5905382364 1.3892651534 0.1008921325 -0.6486318692 [21] -0.0562831933 -0.6887431711 0.4907512082 -0.3994662410 0.7827897030 [26] 0.5294704584 -1.3802965730 -0.6159076490 -0.0009408529 1.6182294859 ...
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