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Articles by Nizamuddin Siddiqui
Page 26 of 196
What is the difference between creating a matrix by using matrix function or as.matrix function in R?
The difference between as.matrix and matrix function is that nrow argument or ncol argument are not helpful with as.matrix function but with matrix function we can use them. Therefore, we can actual define a matrix with matrix function but if we have a data frame or data table then it can be converted to matrix by using as.matrix function.Examples of creating matrix with as.matrix and matrix functionExample1M
Read MoreHow to concatenate two or more vectors in R?
The concatenation of vectors can be done by using combination function c. For example, if we have three vectors x, y, z then the concatenation of these vectors can be done as c(x,y,z). Also, we can concatenate different types of vectors at the same time using the same same function.Example1set.seed(999) x1
Read MoreHow to replace blanks in a vector with the previous element in R?
Filling of blanks is not an easy task in data analysis, especially if the vector contains numerical or integer values. Suppose we have a vector x that contains 1, , 2, 3, 4, 5 and we want to put 1 in place of blank after first value then cummax function along with seq_along function can be used as x[cummax(seq_along(x)*(x!=""))].Example1x1
Read MoreHow to calculate mahalanobis distance in R?
The Mahalanobis distance is the relative distance between two cases and the centroid, where centroid can be thought of as an overall mean for multivariate data. We can say that the centroid is the multivariate equivalent of mean. If the mahalanobis distance is zero that means both the cases are very same and positive value of mahalanobis distance represents that the distance between the two variables is large. In R, we can use mahalanobis function to find the malanobis distance.Example1y1
Read MoreWhat is the difference between ordered factors and unordered factors in R?
To understand the difference ordered factors and unordered factors, it is better to understand them by creating the factor vectors by using ordered argument with TRUE and FALSE options. For example, if we have a vector x then it can be ordered or unordered as factor(x,ordered=TRUE) and factor(x,ordered=FALSE).Example1x1
Read MoreHow to change the Y-axis title to horizontal using ggplot2 in R?
The default direction of Y-axis title using ggplot2 in R is vertical and we can change to horizontal. For this purpose, we can use theme function of ggplot2 package. We would need to use the argument of theme function as axis.title.y=element_text(angle=0)) and this will write the Y-axis title to horizontal but the position will be changed to top.Exampleggplot(df,aes(x))+geom_histogram(bins=30)+theme(axis.title.y=element_text(angle=0))Output
Read MoreWhy do we get warning 'newdata' had 1 row but variables found have X rows while predicting a linear model in R?
The reason we get newdata had 1 row warning is the newdata is not correctly defined. We should give the name of the explanatory variable or independent variable to the newdata so that the model can identify that we are passing the mean of the explanatory variable, otherwise it considers all the values of the explanatory hence the result of the predict function yields the predicted values for the sample size.Examplepredict(M, newdata=data.frame(1.2), interval="confidence") fit lwr upr 1 4.645695 3.690676 5.600715 2 4.459543 3.635161 5.283925 ...
Read MoreHow to save a plot as SVG created with ggplot2 in R?
There are multiple ways to save a plot created in R. Base R provides, metafile, bitmap, and postscript options to copy and save the plots created in R but we can also save the plots created with ggplot2 as an SVG file with the help of svglite package. The ggsave function of svglite package does this job easily and we can also define the height and width of the plot inside this function.Examplehead(ToothGrowth) len supp dose 1 4.2 VC 0.5 2 11.5 VC 0.5 3 7.3 VC 0.5 4 5.8 VC 0.5 5 6.4 VC 0.5 6 10.0 VC 0.5 library(ggplot2) library(svglite) ScatterPlotImage
Read MoreHow to create a line chart for a subset of a data frame using ggplot2 in R?
Subsetting is not a difficult thing in R but if we make our code short then it is a little tedious task because we will have to introduce code between codes and that creates confusion. Therefore, we must be very careful while writing a code inside another code. To create a line with subsetting the data frame using ggplot function of ggplot2 can be done by using subset function.Exampleggplot(subset(df,x1 %in% c("Sample1","Sample2","Sample3")))+ + geom_line(aes(x2,x3,group=x1,colour=x1))Output
Read MoreHow to add or multiply each element of a matrix to the corresponding element of another matrix in R, if these matrices are stored as a list?
Basic mathematical operations such as addition, subtraction, multiplication, and division are common for matrices and we often do that but if the matrices are stored as a list in R then these basic calculations are done differently as they are not direct objects. To add or multiply the matrices in a list, we can use Reduce function with the plus (+) or multiply (*) sign and the list name.ExampleMatrices_List
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