Programming Articles - Page 1732 of 3363

To find the row and column indices of values in a matrix, we cannot simply use which function because it returns the index based on sequence of the numbers in the matrix. For example, if we have a matrix M as below −1 2 3 4 1 6 7 8 1Now if we try to find the index using which(M==1) then it will return 1 5 9Because 1 is placed at 1, 5 and 9.Hence, we need to use arr.ind = TRUE so that the matrix can be read as an array by which function.ExampleConsider the below matrix − Live Demo> ... Read More

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 More

A footnote is generally used to give references to a document, text or image and it is called citation. It helps the reader or viewer to check out the original source using the new text or image is generated. If we want to give citation to a plot in R using ggplot2 package then we can add labs that has caption option to add the footnotes.ExampleConsider the below data frame − Live Demo> set.seed(1) > x y df dfOutput      x       y 1 0.8735462 4.0117812 2 1.6836433 2.8898432 3 0.6643714 1.8787594 4 3.0952808 0.2853001 5 1.8295078 3.6249309 ... Read More

Sometimes we have vectors with NA values, also there might be a situation that one of vector having an NA at a position and the other vector has the numerical values at the same position. For example, 1, 2, NA and 1, 2, 3. In this case, we might want to combine these two vectors to make a single vector. This can be done by using coalesce function of dplyr package.Example> library(dplyr) > x1 x1Output[1] NA 4 NA 1 2 NA 4 1 4 1 2 3 1 4 2 2 NA 2 2 1Example Live Demo> y1 y1Output[1] 1 2 ... Read More

Sometimes we want to determine the multiplication of all the elements of a vector just like the sum. This might be required to test the changes in the mathematical operations that can be applied to a numerical vector. In base R, we have prod function which works same as sum but give us the multiplication of all the elements of a vector.Example Live Demo> v1 v1Output[1] 1 2 3 4 5> prod(v1)Output[1] 120 Example Live Demo> v2 v2Output[1] -0.500466629 0.394771317 0.575743107 0.026982141 0.812697502 [6] 0.995708241 2.198243938 -0.008609976 -0.931337300 -0.073743225> prod(v2)Output[1] 3.228448e-06Example Live Demo> v3 v3Output[1] 1.7328245888 -0.5772304935 2.5161349689 3.0401656274 0.1669773313 [6] -0.0001252235 0.7649984733 ... Read More

In general, the concatenation of numerical vectors and string results in a vector of strings in R. For example, if we want to concatenate 1, 2, 3 with Tutorialspoint using paste function then it will result in a vector as: "Tutorialspoint 1" "Tutorialspoint 2" "Tutorialspoint 3". But if we want it to return as "Tutorialspoint 1 2 3" then we need to use collapse argument with paste function.Example1> x1Output[1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J"> y1Output[1] 1 9 6 3 8 1 8 5 9 1 2 8 3 8 4 5 10 1 6 3 ... Read More

When we create a bar graph using ggplot2, the color of the bars is dark grey but it can be changed to different colors or we can also give different shades of grey to them. This will be helpful if we are plotting a pattern of categorical data. For example, plotting educational level on X-axis with frequencies of years of experience on Y-axis. We can do this by using scale_fill_grey function of ggplot2 package.ExampleConsider the below data frame − Live Demo> x Freq df dfOutput x Freq 1 A 14 2 B 12 3 C 13 4 D 15> library(ggplot2) > ggplot(df, ... Read More

In base R, the barplot function easily creates a barplot but if the number of bars is large or we can say that if the categories we have for X-axis are large then some of the X-axis labels are not shown in the plot. Therefore, if we want them in the plot then we need to use las and cex.names.ExampleConsider the below data and bar graph − Live Demo> x names(x) barplot(x)OutputShowing all the X-axis labels −> barplot(x,las=2,cex.names=0.5)Output

When we perform a t test in R and the difference between two groups is very large then the p-value of the test is printed as 2.2e – 16 which is a printing behaviour of R for hypothesis testing procedures. The actual p-value can be extracted by using the t test function as t.test(“Var1”, ”Var2”, var.equal=FALSE)$p.value. This p-value is not likely to be the same as 2.2e – 16.Example1 Live Demo> x1 y1 t.test(x1, y1, var.equal=FALSE)Output   Welch Two Sample t-test data: x1 and y1 t = -3617.2, df = 10098, p-value < 2.2e-16 alternative hypothesis: true difference in means is not ... Read More

Sometimes we want to combine column values of two columns to create a new column. This is mostly used when we have a unique column that maybe combined with a numerical or any other type of column. Also, we can do this by separating the column values that is going to be created with difference characters. And it can be done with the help of apply function.ExampleConsider the below data frame − Live Demo> ID Country df1 df1Output ID Country 1 1 UK 2 2 UK 3 3 India 4 4 USA 5 5 USA 6 6 UK 7 7 Nepal 8 ... Read More