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Articles by Nizamuddin Siddiqui
Page 194 of 196
How to remove a column from an R data frame?
This can be easily done by using subset function.Example> df df x y z a 1 1 6 11 16 2 2 7 12 17 3 3 8 13 18 4 4 9 14 19 5 5 10 15 20To remove only one column> df df y z a 1 6 11 16 2 7 12 17 3 8 13 18 4 9 14 19 5 10 15 20To remove two columns> df df df z a 1 11 16 2 12 17 3 13 18 4 14 19 5 15 20To remove a range of columns> df df df a 1 16 2 17 3 18 4 19 5 20To remove separate columns> df df df y 1 6 2 7 3 8 4 9 5 10
Read MoreHow to extract characters from a string in R?
We can use stri_sub function in stringi package.Example> x x [1] "TutorialsPoint is the largest online library for best tutorials" > library(stringi) > stri_sub(x,1,9) [1] "Tutorials" > stri_sub(x,1,-20) [1] "TutorialsPoint is the largest online library" > stri_sub(x,-14,-1) [1] "best tutorials" > stri_sub(x,-41,-1) [1] "largest online library for best tutorials"
Read MoreHow to check if a string is a subset of another string in R?
To check whether a string is a subset of another string we can use grepl function.Example> Company Job grepl(Job, Company, fixed = TRUE) [1] TRUEHere we are getting TRUE because Tutor is a subset of TutorialsPoint.> grepl(Company, Job, fixed = TRUE) [1] FALSEHere we are getting FALSE because TutorialsPoint is not a subset of Tutor.
Read MoreHow to access the last value in a vector in R?
This can be done by using tail function.Example> x tail(x,n=1) [1] 1095 > data tail(data,n=1) Class 10 PhD df = data.frame(matrix(rnorm(20), nrow=5)) > tail(df,n=1) X1 X2 X3 X4 5 -0.3595053 0.9943738 0.959761 -0.6565688 > tail(df$X4,n=1) [1] -0.6565688
Read MoreHow to deactivate scientific notation of numbers in R?
We can use options(scipen=999) to do this.Example> x t.test(x, mu=2000)One Sample t-testdata: x t = -14.212, df = 9, p-value = 1.801e-07 alternative hypothesis: true mean is not equal to 200095 percent confidence interval −151.3501 659.0499sample estimates −mean of x 405.2Here p-value is in scientific notation. Now we can deactivate it as follows −> options(scipen=999) > t.test(x, mu=2000)One Sample t-testdata: x t = -14.212, df = 9, p-value = 0.0000001801 alternative hypothesis: true mean is not equal to 200095 percent confidence interval −151.3501 659.0499sample estimates −mean of x 405.2If we want to activate scientific notation again then it be ...
Read MoreHow to change the order of bars in bar chart in R?
This can be done by setting the levels of the variable in the order we want.Example> data data ggplot(data, aes(x = Class)) + geom_bar()Setting the levels in increasing order> data
Read MoreHow to reorder the columns in an R data frame?
Reordering of columns can be done by using square brackets.Example> df = data.frame(matrix(rnorm(20), nrow=5)) > df X1 X2 X3 X4 1 -0.3637644 2.0770246 0.48763128 -0.09019256 2 -3.1758515 2.3173075 0.86846761 0.38396459 3 1.1844641 0.3412267 1.90986295 -1.03493074 4 -0.5953466 1.7211738 -0.90686896 -0.71215313 5 -0.8732530 0.3256303 0.02312328 -0.36993899Let’s say we want to change the order of columns as X3, X2, X4, and X1 then it can be done as shown below −> df[,c(3,2,4,1)] X3 X2 X4 X1 1 0.48763128 2.0770246 -0.09019256 -0.3637644 2 0.86846761 2.3173075 0.38396459 -3.1758515 3 1.90986295 0.3412267 -1.03493074 1.1844641 4 -0.90686896 1.7211738 -0.71215313 -0.5953466 5 0.02312328 0.3256303 -0.36993899 -0.8732530
Read MoreHow to find the index of an element in a vector in R?
There are three ways to find the index of an element in a vector.Example> x x [1] 8 10 9 6 2 1 4 7 5 3Using which> which(x == 6)[[1]] [1] 4Here we found the index of 6 in vector x.Using match> match(c(4,8),x) [1] 7 1Here we found the index of 4 and 8 in vector x.Using which with %in% > which(x %in% c(2,4)) [1] 5 7Here we found the index of 2 and 4 in vector x.
Read MoreHow to randomly select a fixed number of rows without replacement from a data frame in R?
This can be done simply by using sample function.Example> df = data.frame(matrix(rnorm(20), nrow=5)) > df X1 X2 X3 X4 1 -0.3277833 -0.1810403 0.2844406 -2.9676440 2 0.8262923 0.4334449 0.4031084 -1.9278049 3 -0.1769219 -0.1583660 -0.2829540 -0.1962654 4 1.0357773 0.9326049 0.3250011 -1.8835882 5 -1.0682642 -0.6589731 -0.4783144 -0.2945062Let’s say we want to select 3 rows randomly then it can be done as follows −> df[sample(nrow(df), 3), ] X1 X2 X3 X4 2 0.8262923 0.4334449 0.4031084 -1.9278049 1 -0.3277833 -0.1810403 0.2844406 -2.9676440 5 -1.0682642 -0.6589731 -0.4783144 -0.2945062
Read MoreHow to rename a single column in an R data frame?
We can do this by defining the newname as shown below −> Samp Samp sample.1.100..10. 1 47 2 63 3 57 4 16 5 53 6 7 7 54 8 2 9 13 10 14 > colnames(Samp) Samp Sampled Values 1 47 2 63 3 57 4 16 5 53 6 7 7 54 8 2 9 13 10 14 Since we only have one column in the data frame, so it is sufficient to use the object name.
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